What about unity? If you are proficiently with it, is that a good signal or not?

Unity is used by so many studios, it's a great signal if you're joining one of those and probably a good signal for Unreal shops as well. I think knowing C++ is a more robust signal for senior technical roles but I don't think it's a silver bullet for every role.

I would prefer engine experience over language experience if wanting someone to join and get to work quickly.