He's been pretty much what they expected. Note that they signed him for three years guaranteed (team option in 2022) at small money - it's a development contract, not a make-good contract.
He creates 3-pt shots off the dribble with either hand. Quick release, has side-steps to either side, and most important he's not afraid to let it fly. Has a fake and dribble move into a midrange jumper that's usually open with today's defenses; and he's got a real chance, with his stroke, at becoming one of the rare players who can be productive from there.
Where does he wind up in the judgment of NBA history? The upside is Isiah Thomas with better defense. The big middle of the bell curve has comps like Terry Rozier, who can create lots of shots for himself, not at an awesome percentage, but with an ability to hit clutch shots.
I've said before about his 3-pt%: it's not a lot of shots. Mechanics and stroke are really good and he squares up and lets it go really quickly. He's got the handles to get open. You can be confident that the threes will be a strength.
Good lower body strength and reflexes. Sounds like his determination and intangibles check out.
Less certain is getting to the rim and finishing; and if he really is going to attain IT nirvana he'll have to find his way with that. That's the thing that you need to track next season; that's the difference between a specialist on the outer rungs of a rotation and a sixth-man.