IM just curious but lets say you attack a state that has others annexed
do those annexed states stack onto you or are they liberated
it's up to you to liberate, annex, or form a personal union
however, if the state is controlled by a player, you can only form a personal union (it will still count as being under your empire, however)
some casus bellis will require you to go only one way, though
some will demand full annexation, for example