I'm still waiting on some of the total conversions to get more developed, so I tend to stick to QoL mods. Here are some of mine:

Community Flavor Pack

Extended Outliner

Clear Notifcations

In My Humble Opinion

More Interactive Vassals

Great Empire Wars

Prisoner's of War

In My Humble Opinion adds the ability to see what your current character links of a character you're looking at - just like in CK2 which is great for some quick RP

Prisoner's of War is a great small additional in which characters taken captive in battle don't just teleport to the war leaders dungeon and are instead held by the capturing army until the make it back to their borders.

What are your favorites???