These are in my opinion (and in the opinion of a lot of other people) the best mods for CKII.
3.the prince and the thane,
the prince and the thane keeps the same timelength and map as the vanilla CKII only it ads so much to the game! for example , you have a lot more buildings that you can build in your holdings , and they are now more realisticly with their tax income , for example there are some that reduce your income.
there are a lot more events , for example the crowning event , when your ruler dies and you continiue as his son , then all the vassals must go to the capital to pledge their loyalty to you , sometimes however they might decline , in wich case you can declare war or let them become independant.
2.AGOT (a game of thrones)
this mod recreates a game of thrones map and system , It gives you various time periods wich are accurate to the book trillogy, and also the events that happen in the series,.
it creates manny new traits and buffs , many new events for personal interaction and a lot more new features.
Elder kings is a recreation of tamriel , or if you don’t know what I’m talking about , the continent that skyrim lies in.
This mod ads all the races of the elder scrolls , ads all the countries , and starts you og before the cyrrodillic empire is formed .
This mod features a lot of new traits , events , races , cultures , religions , descisions , casus beli , continents ,and also ads mages as a infantry unit.
In short , this mod is awesome and at the very least deserves a look.
These were the 3 best CKII mods , hope you check them out , and enjoy!