It's way too early, but just for the sake of being dumb and overreacting I'd say CJ is obviously looking the best so far, while Young is looking the worst.
BUT, Young is possibly still injured so who knows...
I think Richardson is going to continue to play his own style and forge a different path than Stroud, and that's okay.
Rejoice Texans fans, O'Brien can no longer hurt you. They just might have finally figured football out enough to have some sustainable success for a while. The AFC South might be in trouble.
TLDR: At the quarter mark Stroud is doing great, Richardson is fun to watch, and Young is struggling.