Rule tweaks and changes
Home Region Movement Bonus
If you're sick of enemy forces raiding your provinces then giving you the runaround when you finally march out a doomstack to take them on, this mod that gives a +10% bonus to armies moving across their own territory should sort that problem out quick smart. If you're playing as a horde like the Warriors of Chaos or Beastmen this won't do anything for you, since you don't count as having a home. Poor wandering monsters.
No Aggressive Agent
The AI loves using heroes to assassinate your lords, block your armies, sabotage your walls and generally be a nuisance. While you could train up a couple of heroes of your own during the early game so that by the time enemy agents show up you can assassinate them the way you're supposed to, you can also just install this mod that prevents them from attacking. As with the outdated mod this replaces, you'll still be able to conduct your own hostile actions since that's necessary to trigger certain quests and resolve grudges.
Walls for Settlements and All Races
Total War does conflict in open fields well and defending a great big city from behind its walls is fun, too. For anything in between it's a bit rougher—maneuvering units of Napoleonic horsemen down narrow village streets was never exactly a joy. Total War: Warhammer avoids this by turning all battles over minor settlements into The Great Outdoor Fight, but if you'd like more sieges this mod gives every settlement at least some low walls to hide behind.
Each of Total War: Warhammer's starter factions is set up in opposition with another, only able to occupy settlements belonging to either that opposition or their own kind. That leads to some interesting differences between the campaigns and encourages more sacking and razing, but if you really just want to paint the entire map your color then this mod will let you settle anywhere.
The Uncivilized North
The Norse Vikings gain depth with The Uncivilized North, which adds new tribes and differentiates them from each other with unique bonuses, but mainly makes them a lot toothier. The Norse will now go to war with each other as well as anyone they can reach by longboat. You can play the campaign as them if you like, but since this mod alters the starting position be aware it may cause conflicts.
Armor Piercing Pistols
In tabletop games of Warhammer, firearms have a bonus to their armor-piercing quality, reducing their targets' saving throws. In Total War: Warhammer the guns carried by pistoliers are more of a nuisance weapon, their shots tending to ping right off armored enemies. This mod beefs them up.
Ever autoresolved what should have been a trivial battle and realized that although you won one of your best units is now gone? Sometimes the autoresolve will rob you of one of your Giants or other more powerful units if it starts a battle at less than 100% health, and you can either fight all these pointless skirmishes yourself to ensure they stay safe, or subscribe to this mod.
Chaos Please Wait
If you'd like more time to make peace with your neighbours and confederate their lands or just grind them under your heel until nothing but dust remains, Chaos Please Wait gives you that time. Depending which faction you play you'll have about another 100 turns of expansion and empire-building before the Warriors of Chaos finish psyching themselves up by listening to doom metal albums and finally march south.
Greenskins Teef Currency
The Vampire Counts faction get their own currency based on dark magic, which somehow has a one-to-one conversion rate with the Imperial Gold Crown, but the Greenskins are stuck with generic coins. Several of their events refer to their actual currency—the teeth they knock out of opponent's skulls or just yank out of their own if short of cash—but this mod alters the UI to call money 'teef' as well.
Warhammer Revival: Wood Elves
The first in a series aiming to accentuate what makes each army feel special, Warhammer Revival makes Wood Elves more accurate at archery, though leaving their range the same to suggest that it's the archers rather than the bows doing the work. It also adds special rules to other units to make them faster and harder-hitting, though no more survivable. (A compatible mod, , improves the stats of Wardancers while also increasing their cost.)
Warhammer Revival: Beastmen
Warhammer Revival: Beastmen, which benefits from also having Warhammer Revival: Wood Elves installed, does something similar with the Beastmen – beefing up their Fury-related abilities so they seem more bestial and out of control.
Loreful Diplomatic Affinity
If it bugs you that Dwarfs regularly wind up at war with their own people, Loreful Diplomatic Affinity reduces the likelihood of that. While it makes factions of the same culture more likely to get along, it leaves some of them distrustful. The staunch northerners of Middenheim will never really get along with the rest of the Empire, and the forest spirits of Argwylon will always be wild. Be aware that if you change your mind about this mod you'll have to start a new campaign, as it can't be disabled halfway through.
The whole point of Night Goblins is that they hide Fanatics in their units, tiny maniacs all hopped up on mushroom juice with oversized ball-and-chains they spin around as they leap out of an ordinary-looking unit of archers like a lady from a cake. Sometimes though they just twirl around a few times and then fade away. This mod ensures they stay on the dance floor for a few more spins, and since their movement is random and it's possible they'll turn on you, it's not too unbalancing.