EAWX is the biggest, excels in scripted mechanics that tilt the game more toward 4x. resource management, faction mechanics, planet loyalty, etc. it's more barebones than other space strategy games due to modding limitations but they try to make the best of it. currently they've got a legends-canon mod following the battle of endor & a clone wars mod following the cartoon with legends add-ins. and soon they'll release the first fully functional KOTOR-era mod, ever, it's very exciting since like 3 other projects didn't make it out of beta

AOTR is basically the setting of the original game but with its own brand of expanded complication and content. i really like their ground combat, they figured out making the infantry a modern and potent component of forces (integrated support weaponry, among other changes). it's really hardcore^tm though so not beginner friendly

Rise of The Mandalorians is a completely finished expansion-style mod that dropped in 2019, it fully replaced & revamped i think, everything in the game actually. it's also exactly the style of the original game despite some important technical innovations these other mods ended up using. it's a very cool comparison as a love letter to the game in full, instead of how these other mods try to wrestle the game into things it wasn't really designed to do.

Third Age Total War you've already heard of it, everyone has. before we had Fantasy Warhammer sucking up all the development at the Creative Assembly, we had Third Age sucking up all the oxygen on the total war forums. it's so old and was so extensive when it dropped that it's easier to think of as a base-game in its own right, for which there are dozens of sub-mods. most major is probably Divide and Conquer, which makes the map a lot busier and exciting in all the corners. its also gone through so many developers that anyone who's played it a long time probably has a couple of faction designs they miss (white-armored samurai variags squeaky's dorwinion ) then there's Last Alliance, which takes you to that 5 minute prologue bit at the beginning of Fellowship and goes pretty buck-wild with the faction designs that didn't appear directly in that movie sequence---bronze age coded wildmen & rhun. it's pretty fun but suffers from similar problems as og Third Age regarding boring parts of the map. there's a few more big projects but i wouldn't call them totally playable (Silmarillion, Reforged)

Stainless Steel is a similar heavyweight, its last mainline release is still a good expanded version of the original game that doesn't depart too far. but my god the submods & things built upon it. i don't even think you can list them there's so many. Bulat Steel is a major russian one that is semi-famous for extremely detailed units, they also helpfully install the entire original game for with it

Tsardoms is the most finished and historically accurate mod out there, i'm an enormous fan, it's about the rise of the ottomans, can't recommend it enough. Balkans, Anatolia, Italy they even have 2 separate releases, one for experiencing the precipitous decline of the roman empire in the 1340s and one for dealing with an already gargantuan Ottoman empire from its peripheries in 1450s

Broken Crescent is old and not too historically locked in, which is a shame because its the best mod with a focus of western asia, one copes with it by adding in units from other mods so it looks more up to date

some would say EBII is super historical and fun too and to that i say EB projects version of 'fun' is punishing players for having it but fr it doesn't run very good, its map is full of empty space like RTW and all the shit they put in to make it hardcore and historically accurate just makes it a slow slog