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.
Absolutely! Each of these fit really well into the "spirit" of the game. I think Great Empire Wars and More Interactive Vassals are more varied but create a much more dynamic and interesting experience.
I added them all last night. I'm part way through a playthrough so I'm not sure how much of a difference that makes, but I'm really liking Community Flavor Pack and Prisoner's of War. Having to move prisoners and commanders around is great. I'm also playing in Africa at the moment, and the flavor pack has really brought the area to life!
Weight of the crown is a mod originating from the Chinese community that very ambitiously represents minority cultures/religions, and estate powers in government. The English translation is not perfect, and this mod does slow down the game a little, but I believe it does all it wants to do in a spectacular way.
I originally bought ck3 solely for elder kings 2. I prefer the original game over it now, but it'll always hold a special place to me for pulling me in, lol
AGOT is a must-have for CK2 if you're a fan of the series. The mechanics it adds are great and I barely play the vanilla version anymore. Can't wait for the dev team to port it to CK3!
VIET and also RICE are great for this. I think VIET is mainly/mostly general flavor events while RICE adds stuff to specific regions and includes decisions. In combination they can really make the gameplay more varied from a vanilla run.
Although when I checked earlier this week one of both of them hadn't be updated for 1.9.1