If he's not on roids then that's about near the limits of human size and performance without them or puffing up on protein shakes. I'm no expert but his neck and jaw look normal and he doesn't seem to have crazy roid eyes. So that's a good sign!
He's a pretty small guy, he has an average amount of size for an athlete, just (very) low body fat. And if you watch enough of his videos you'll find he takes sunwarrior protein supplements.
No reason to think he does steroids, but he is pretty freaking strong.