I'd propose you 2 threads :
https://forums.civfanatics.com/threads/recommend-a-modmod.535928/
and
https://forums.civfanatics.com/threads/best-current-ffh-setup.620660
but in short:
MnAI worked a Lot on improving the AI behavior and hunting bugs while staying as close as possible to original FFH2. It is the "purest" modmod. You can almost consider it to be FFH2.1. No added units/buildings/spells/ressources/civs...etc
FFR is the one that you have a question for: RifE / AoE / FFR are all iterations of a same modmod, expanding upon the work of the one prior when the previous modded leaves. In Short FFR adds FLUFF : many new civs, new ressources, more unique units per civs, more buildings, more tech(?), more mecanics (adding in the corporation mechanics from vanilla civ ; the master-craftsmen buildings ; the emergent Leaders ; using the Commander system instead of the Great General system, wildlands and barbarian territories, fort commanders ...Etc). AI wise, the Ai has been less polished than in MnAI and it has further issues with managing many of the newer or more original systems.
+FFR/RifE is modular so you can add/remove some contents... which is great for variability of games and for customizing your experience.
for reference:
the best one for extra fluff is IMO Orbis : Adds a few civs but not too many, quite as balanced as original civ. AI is decent even if not to paar with MnAI (but it is the oldest of all the mods I'll cite here: it has been "finished" instead of abandonned, and is quite good) only issue is that it is old and couldn't benefit from the AI and balance improvement of MnAi or EiTB
EiTB worked on balance, especially in view of multiplayer, and chasing multiplayer/synchronisation issues. There are the same units& civ as in MnAI, but with many tweaks of hammer costs, tech requirements...etc
Emm is based on MnAI and introduces to the AI improvement of MnAI the balancing of EiTB + a bit of fluff.
WildMana: add fluff, but mainly for improving the magical system adding mana guardians...Et ; it is quite interesting. (but quite old as the modder tansitionned it later to MoM)
Master of Manan or MoM has very nice system and AI... but it's almost a total conversion of FFH2 : most mecanism are changed : I'll suggest you to play with version 1.42 and X-tended for 1.42... (or maybe
Darksavant's modmod... which has the better Ai, many interesting things and bug fixes of beta2 but do not use the roosters and planes, which are currently not-finished/balanced)
However, please beware, while lore is very close to FFH, the mechanics make it a totally new game... as far from FFH than FFH is far from BTS.
(NB: version beta3, which is now abandonned, seems interesting, but very complexe, and even more different from base FFH)
Eventually, Magister's modmod is also a "new fluff" game, it adds a lot of mechanics and changes to units, spells, buildings ...Etc but no new civ. It gets the improved AI and Balance from MnAI. Its philosophy is to make the game closer to "cannon-lore" than it previously was, even by adding new mechanics, some of which are really complicated to code) Further it pushes even farther the main concept of FFH : "Balances is reached by powering up a weak party instead of nerfing the strong ones" : Balance in Magister Modmod is made my creating many ways to get OP...
