300+ of anything past level 40
200+ if party consists entirely of Noldor (good luck)
So far as I have ever been able to tell, battles out in the field are generally won by copious amounts of powerful cavalry, and sieges are generally won by a good mixture of archers and shield infantry.
There are exceptions, of course. Strong enough cavalry doubles as shield infantry in sieges, and strong enough archers (Usually involving Noldor Composite Bows) and infantry (Ebony Gauntlets) can be powerhouses on the field. Incidentally, no amount of even numbers is going to let you fight against Demonic Magnus' or the Noldor unless you're fielding entirely CKO troops on Day 1500
I don't know if things have changed, but I know a good number of people who, whenever they decided to take a walled fief without being a vassal to start their rogue kingdom, would generally just field a very large amount of Ravenstern Rangers or better archers, let them shoot at the wall til they collectively ran out of ammo, retreat, siege again. I don't know if people still do that.
The mod is filled with powerful troops that are (mostly) well balanced, so it's pretty much just finding which ones you like best.