Off the top of my head, the arena mod makes 'training' your troops a thing, by bashing them about in the arena. I liked it because I could pretend I was actually training my army.

I know there were several others I used, including an execution mod that makes it so enemies of a lord you execute are happy with your decision (rather than every single lord ever suddenly hating you), a politics mod that makes other nobles more 'realistic' in their moods and desires, and one that changed the max level you could get in a skill based off of points invested in it.

There might have been one that added a 'missile barrel' that you can get more arrows from in a siege, but I think I'm confusing bannerlord with warband on that one.