Here are A few general rules that govern how A planet forms

Planetary Atmosphere
Three factors play into a gas's ability to escape the pull of a planet's gravity: temperature, molecular mass, and escape velocity (the speed a molecule needs to achieve to escape into space). Hotter, lighter, and faster particles more easily slip out of a planet's gravitational grip into space than cooler, heavier, and slower particles.(so special equipment would be needed to retain any atmosphere of size on small worlds. or Dome structures.

Gravity
Gravity is Going to be an issue for any creature that moves through it's enviorment in anything but A horizontal fasion,By this I mean the further your center of gravity is from the ground ,the more gravity is going to be an issue.
A flat organism on a high gravity world would not have much problem ,but something like A human whom walks upright
would find it rather difficult to move about on a planet say 3 times as big as earth .

Distance from Parent Star or Star's
There is A "zone around any star where Water would exist in its liquid state .Any closer and it boils away,Any further and it freezes .

Multpile Stars and Stable orbits
We probably owe our existence to the fact hat the Sun is A single Star ,and almost all our Planets orbits are fairly circular.  This is very important in regards to climate. A circular orbit will give A fairly stable climate year round. there may be A tilt of a planet's Axis Causing slight climate changes. like earths seasons,but these changes are only by A few degrees and not all that drastic.
an eliptical orbit or even more distorted orbits are seein in multiple star systems .These planets see temperature changes in the ranges of 100's of degrees ,going from -200 degrees to well above 700 degrees in the span of an orbit this would be fatal for life as we know it. but thats not saying life could not find a way to go dormant for the harsher part of the orbit .(there are organisms whom create their own antifreeze)

So with these things in mind lets apply this to what kinds of bodies there can be possible

you have 3 temperature types we will seperate them by their water state
then you got the planets actual composition,its distance from parent star would vary in accordance to the existance of liquid water depending on the actual stars type(The habital zone of A blue supergiant would be much larger and farther away from the star as the habital zone of say a red Dwarf .)lets just worry about its composition and water state for now. then we can apply some penalty's and bonuses to each type in sins .
A bodie must be a certain size to copmpress into roundness. right around 300-400km across . this size figure would decrease the more icy the body is as it is easier to move ice around than it is to move rock,and of course a gas ball would compress at even smaller sizes. probably around 100km to be round

the notation of water or no water or ice is purely A matter of where the planet developed .not all planets will contain water.this just lists the posibility of whether it could contain it .as water is a very volatile substance and readily evaporates or boils or binds with substances so although water could pool on a medium asteroid it would be vaporized and dissipate rather quickly

                                                         Of Atmospheres And  Planet Cores
                   the possiblilty to have a molten core and hence A magnetic field would arise on worlds
                    approaching this size .  One thing to note now that we have gone this far is age.
                   Atmosphere and molten cores are not permanent.the older the system the less likely there are gonna be                    terrestial atmospheres and terrestial magnetic fields. A gas giant would last far longer in both respects                    than a small earthlike planet.  Large things cool quicker .No mol;ten core and you got no mag field which                    consequentially now makes the atmosphere go bye bye even faster . solar radiation will burn an                             atmosphere away pretty fast at distances where water would be liquid,in the absence of A protective                          magnetic field  that is channeling all that harmfull solar radiation away to the planets poles.



                              Freezing /Cold                      Liquid /Warm                             Hot/boiling

Small asteroid         Low grav/Ice/rock/     Low grav/No Water/rock                    Low Grav/No Water/rock
    1-10km              No Atmosphere /         No Atmosphere/                               No Atmosphere/
                             Not spherical              Not spherical                                     Not spherical 


Medium asteroid      Low grav/ice/rock/      Low grav/No Water/ rock                  Low grav/No water/rock
   10-99km             No Atmosphere/           No Atmosphere/                              No Atmosphere/
                             Not spherical               Not spherical                                    Not spherical

          Here is the cutoff point where a planet has sufficient gravity to compress into a sphere


Large asteroid         Low grav/ice/rock/      Low grav/No water/ rock                  Low grav/No water/rock
  100-299km           No Atmosphere/          No Atmosphere/                              No Atmosphere/
                             No mag field               No mag field                                    No mag field
                             Spherical if ice             Spherical if ice                                Spherical if ice   
      
ProtoPlanet           Low grav/ice/rock/      Low grav/Water/rock                        Low grav/No water/rock
  300-400km          No Atmosphere/          No Atmosphere/                              No atmosphere/
                           No mag field /              No mag field /                                  No mag field/
                           spherical                       spherical                                         spherical
                     
                           all planets this size and up are spherical  and are just noted with A  /S

  Tiny Planet          Low grav /ice/rock/    Low grav /Water/rock                       low Grav/No Water/rock
  400-800km          No Atmosphere /        No atmosphere/                               No Atmosphere/
                            No mag field /           No mag field/                                   No mag field/
                            /S                            /S                                                    /S

Small Planet         Low grav/ice/rock       low grav/water/rock                          lowgrav/No water/rock
  800-2999 km       Possible Atmosphere/  possible Atmosphere                    no Atmosphere or light /
                           No mag field/              No mag field/                                   no mag field/
                              /S                              /S                                                     /S
                                                                                 
 (earths diamiter is 12756.1 km )                 
Medium Planet      1/5th-earth grav          1/5th-earth grav                              1/5th- earth grav
                           Atmosphere   /           Atmosphere   /                                Atmosphere/
3000- 14999km    Ice/rock                     Water/rock                                     Rock
                           mag field                    mag field                                       mag field
                             /S                                  /S                                                  /S

(not yet A gas giant)
Large Planet           2-5x earth grav        2-5x earth grav                                2-5x earth grav
 15000 -24999km   Atmosphere             Atmosphere                                     Atmosphere
                            ice /rock                   water/rock                                       rock
                            mag field                   mag field                                        mag field
                             /S                                /S                                                /S
     
                               From here on planets are Gas Giants and the larger you get ,the morestarlike the planet
                                becomes  ,up untill the point where it undergoes nuculear fission in its core. which is around 87
                                 times jupiter's mass or 27,666 earths so we are only going to deal with gas giants and not go
                                into planets much larger than 10 times jupiters mass. these giants would be very violent
                                neighborhoods anyway due to their large and powerfull magnetic fields and swarms of
                                charged particles orbiting it

Gas giants          5-50 times earths gravity  all will have thick atmosphere ,high speed winds,large magnetic 
                         fields,many moons ,  Water is probably present but only accesable from moons.




So what does this all have to do with sins?


well i am designing planets  that have properties that affect gameplay based on these assumptions so he goes some examples.


there will be new sub types of each planet type

Terran : 

Island planet,Tundra(icy),Desert(barren),Dense Atmosphere(venuslike),Forest,Swamp,Primordial(prehistoric earth).giant (high grav earth)

Ice :

frozen comet,comet,ocean core(slushball),frozen asteroid,Methane volcanic.

Gas giant  :

Huge earth(think a bit smaller than neptune) ,Jovian(jupiterlike),Protostar(almost a brown dwarf)

Plasma Storms :

I place these around my stars to simulate solar flares and prominences .

Magnetic clouds I place around my gas giants to simulate the clouds of charged particles surrounding these bodies .

Wormholes:

Although the Idea of wormholes does not sit well with my theories of the universe ,I use these as my sole connections
to other stars,     

Stars  :

In my Galaxy's There are no connections to stars ,rendering them as just a pretty ball, Logically speaking ,Approaching A Star at even A modest distance. (say one or 2 solar disk's distance away )becomes a suicide mission
There simply is to much violence surrounding this reigon in so many different forms that approach would be unlikley,so i eliminate star travel altogether and use the plasma storm as my near star rout s around it.

Now Assignig values to things like gravity strength,temperature ,magnetic field ,shape,size ,planet type is A balancing issue And needs to be tested before any real numbers would be useful ,but changes to population growth,population cap,tax rate,tactical and logistical slots,Health,Gravity well,And all that other stuff i am trying to work in.

So if anyone has A thought. a comment , Whatnot I Would surely apreciate any feedback.