Thomas is small, maybe 6'3" without shoes.
He has a decent handle and is a good and willing passer. In the limited minutes he has played, I note he hesitates to take slightly contested shots, even if he is fairly open. He needs a better mindset as he tends to make the contested shots he takes. He is a really good shooter.
He has horrible defensive footspeed. Toronto often played zone to try and hide him on D, but he can't even recover in his zone. One on one he gets easily burned. Toronto is near the bottom in defensive rating as I recall, and Thomas still can't get on the court, his D is that bad. Can it be fixed? He can become a more fundamental/smarter defensive player, but you can't teach length or quickness. Gobert may provide the shield he needs on D to let him stay on the court. I could see him averaging 12-15 point in the Jazz system if his liability on D doesn't keep him on the bench. I do think his D is so bad that this move will not likely pay dividends for the Jazz. I hope I am wrong.
Hughes is a better prospect IMO.