I wonder if there was a specific reason they didn't give The Grand Inquisitor the elongated head that the animated version and all of the other Pau'ans we've seen have? We first saw them in Revenge of the Sith with those heads, so it's something that they can do in live action, and isn't a animation only thing.
Rupert Friend is a noted and successful actor. So they went with a known quantity instead of just a rando with a narrow head. But, yeah, it definitely looks weird!