Tbh I don't know that Castle has a huge bag on offense, and that's even as a range threat. He can finish lobs and cuts pretty well, but the thing that makes him a great defender, his methodical, careful movement and positioning, is kinda the same on offense. He's not that quick, little blow-by, has to bump and spin to get around defenders to get to the bucket. He's decently athletic on the run but doesn't have a ton of pop otherwise.
That said, Pop's offense is predicated on quick moves, reads, and so on, and he's certainly capable of that.