Let's all just keep in mind that Doug McDermott and Anthony Morrow also looked really great in summer league.
Guys with great jumpers and deficient strength and athleticism often look nice in Summer League.
The question is, can RJ get open against NBA competition, and can he avoid getting torched on defense? Can he hit shots with quality defenders in his face?
I think what separates Hunter from Morrow and Doug is his ball handling and passing. He's very good at making the right pass and shows signs of becoming a good secondary ball handler.
Can he hit shots with quality defenders in his face? No, his release is too low, he's not a good contested shooter (yet, hopefully...). But with, let's say, Thomas driving to the basket and kicking it out if the defenses collapses, he'll be perfect right away. So I anticipate him getting some minutes right from the start.
Can he avoid getting torched on defense? I think he can. He may not be fast enough to keep his opponent from getting by him, but he seems very intelligent, so I believe he'll find a way.
And I agree, his ball handling and passing will compensate his limited offensive contribution (if he doesn't get open shots) or some problems on D.