Ceiling: better version of John wall
Floor: cj mccollum
Fultz has a better shooting than wall and kyrie. Fultz has better rebounding and passing than kyrie, lilliard , and roy.
I don't see Wall (or Westbrook for that matter) at all, he just doesn't move at that pace. He projects to be a better shooter though. He's certainly not a better shooter than Kyrie Irving either.
The Harden comp is the best to me, he's got the same crafty game and pace. He can push it, but is often content to take his time and probe. He's not as heavy as Harden, and seems like he's more athletic. We'll see if his game develops as well as Harden's has.