I’m gonna go ahead and say that Voudon can’t join at game start due to the way its ability interacts with Vortox. Detailed reasoning below.
“Only you and the dead may vote on executions” means that on the first day, where no one is dead, only the Voudon may vote on executions, so an evil Voudon has gamebreaking potential because they just don’t vote anyone to try and trigger a D1 Vortox win.