about all of them, cause vb4 uses a new code's to interact with the database and user.
so they most likely wont work.
mods such as BBcode which arent mods, will ofcourse always work.
admincp mods only also works, but as soon as they present something or make
a change for the user 95% wont work.
95% cause im using atleast 3 vb 3.8 mods on my board, that works and 1 3.5 mod.
But in short mods and styles from vb3 wont work for vb4, with a few exceptions.
So yes, remove them all.