Carrier Battles Mod is very very different too.
No AIs, but I've got PBW games open (both competitive and newbie games).
Overall, CBmod has an aura of honorable, stand up combat.
It has significantly less "stuff" in it than stock (components, facilities, hulls, etc) but each item is finely tuned, so there is infinitely more variety in gameplay.
No mines, leaky shields and armor, leaky PD which almost never gets them all, but hits more often when there are a lot of missiles.
For example, there is no "best" weapon. Mixed fleets are basically required. Without a proper balance of heavy missiles, light missiles, light torpedoes and lasers for PD, heavy short-range DF, and lots of dogfighers, interceptors and bombers to fill out your ranks, you are vulnerable.
Some long range heavy torpedo boats don't hurt either.
War in CBmod is brutal, gruelling and bloody. Even when you win, you can expect very heavy casualties. And casualties in CBmod are quite often due to cripplings, not vaporizations.
In CB#2 on PBW, the last two players standing had a nasty melee in a central system. When it was over, both sides were left with 30% of their navy stuck in parking orbits at the repair yard facilities behind the front lines
All of the cultures are playable, even though they are wildly different in effect.
You can get everything from 2x-build-rate "Disposable Societies" to the maintenance-free "preservationists", to the good 'ol Berzerkers, and the egg-head "brainiacs".
In fact, in CB#3, we have both a "Preservationist" and a pair of "disposable societies" in the same game.
There is a "Hard workers" player buffering the two so the disposables haven't managed to kill off the P's early. As the game progresses, those Preservationists will become ever more powerful, and eventually have some nice, big, maintenance-free, stomping fleets.
Gonna be interesting.