I'm looking to have too puppets act in unison, like twins. Is it as simple as copying and pasting the timeline from one puppet to the other? Or do I need to do something different?
It might sound like a trite answer, but I would try it and see. E.g. if the puppets have different behaviors etc, then it might not work. So without having your actual puppets and trying it, I would not be confident with a response.
The other thing you can try (to some extent) is activate both puppets in the timeline at the same time when you record. Its not going to be perfect (e.g. if using draggers), but the camera and triggers I think will go to both puppets the same.