I think he has the same issue Timelord did when he first came into the league. He's looking too much for the big blocks. Obviously doesn't understand the Spurs' defensive schemes yet so he struggled in rotation and switches. He can protect against drives, but I think he will get hammered on post ups until he puts on more weight...at 209 pounds he's like a leaf. I can just imagine Embiid breaking him in half. Though I doubt he would ever switch onto him until he gets stronger.
The offense is a work in progress, he's obviously got some sweet touches and has good vision as a passer, he should find his range soon. Seemed to be forcing things tonight, I'm sure Pop will figure out ways to maximize his impact on that end. But still pretty raw. I really think he needs a year to bulk up. Comparing him to Banchero, Paolo had a much more NBA-ready body and was able to make a big impact right away. But Wemby's only 19 so it's all in front of him.