As a Tennessee fan, I've been following Stokes with a lot of interest over the last month or so.
He's a big, strong dude - 6'8" 250 with a size 20 shoe. The thing that has stood out to me through his three games so far is his natural ability. He can score from anywhere, has a smooth jumpshot, very solid post game and will drive if he sees an opening. Great hands, excellent rebounder, surprisingly good passer, puts in the effort on defense (although he doesn't know the defensive system all that well yet).
I expect the free throws to improve. He's a good shooter, and I see a lot of unnecessary movement in his free throw routine - trim that down to a more repeatable motion, and he'll be fine there. As I said, he'll drive when given an opportunity, but his handle is a bit loose at this point - he'll get his pocket picked from time to time if he tries to do too much dribbling.
He'll never be an athletic freak, but I also think he's considerably more athletic than he's showing now - this is a kid who didn't play ball in his senior year in high school, so these have been his first three 'real' games in a long time.
I don't know what his ceiling is. Physically he has his limitations, but his versatility scoring the ball makes me think that he can be more than your typical undersized backup PF. If he grows a couple of inches in his college time, look out.