For starters, I´d recommend the Bug Fixer (because that´s what it does - it fixes bugs) and, if you want a bit more of a challenge in battles, the Darth Formations for vanilla. I very much like that combination, because, basically, I happen to like the vanilla game.

I can´t really give advice on what mod to use, so far I haven´t used any mod to replace the vanilla gameplay -I do use Chivalry, Citadel, LotR and METW, though, but that´s because they are completely differently themed.

Don´t expect wonders from any mod, though, there´s only so much modders actually can do.