Jaylen Brown will end up, 90% sure, as a poor man's Kawhi Leonard. 15 pts, 5 reb, 3 ast. There is a 10% chance he could become close to Kawhi, as good as Kawhi, or slightly better imo.
The qualities that make him relatively high ceiling- NBA ready body at 19, intelligence, attitude, defensive ability (except that he seems to fall for pump fakes too often) and athleticism.
The quality that could make him a bust: has very little feel for the game.
His shooting is nothing to worry about folks. He will never be elite shooter, but he doesn't have any hitches in his shot and his form is pretty good. He has already improved that shot since his time in Cali and by the time he is 22-23 he should be a good shooter.
However, the feel definitely worries me. It ends up in lack of control, bad passes, bad shot decisions, etc.