Anything counter-intuitive I need to know?

Vassals operate according to game mechanics and not psychology: during a civil war, you are often best advised to let your disloyal vassals go free or force-vassalize them without removing their titles until the worst is over. This keeps your badboy score low.

Many events operate across borders. Land borders are usually self-explanatory, but over seas there are only certain specific trade lanes (usually connecting major ports.) For a map, see here.