What is the best mod for a MP orientated player?

Define "Sins experience".  Are you looking for different races, different gameplay?  Distant Stars has the same Sins factions, but greatly expanded research and buffed starbases and capitals with additions like planets having passive buffs on their gravity wells and expanded strikecraft choices.  Enhanced 4X adds more 4x features to Sins of a Solar Empire, and comes with mini-mods to disable superweapons, expand research, and reset Titan levels on death.  Interregnum does all that, and adds the Galactic Empire from Star Wars as a playable faction.  Sins of the Fallen adds a ton more races to Sins, including the Cylons and Colonials from Battlestar Galactica.  Sins of a Galactic Empire is a total Star Wars conversion that plays nothing like basic Sins, and requires a hefty adjustment period.  All of those mods tend to be pretty balanced as they're played extremely regularly, and Distant Stars actually nerfed Disruptive Nanites before Ironclad did.

I meant to say a mod that is not merely a "balance patch" for the normal game. I could also add that I would prefer mods that focus more on RTS features than 4x.

I don't think you will like Distant Stars, it has no balance whatsoever...you probably should just go for one of the total conversion mods, the Star Wars one (SOGE) is cool and I've heard the Star Trek and Halo ones are pretty good...

Star Trek: Sacrifice of Angels 2 has very OP Borg, so if you play as Borg, it should be against a team of 3 or 4. If you play against the Borg on a FFA, diplomacy is the key, get allies fast.

Even total conversions like SOA2 still are a mod of te original game, so the RTS and 4x are still very dependent on one another.

Sins of a Galactic Empire is probably the best bet for being the most balanced and faster paced of total conversion mods