Brown is longer, that's about all he has on Hayward. Hayward was a great rebounder at Butler.
I'm higher on Troy Brown Jr. than most. I think he can mix some of the versatility of Hayward with the toughness and mid-range game of Jimmy Butler if he puts it all together. He's got really good vision, decent IQ, good defensive instincts and an underrated ability to score from mid-range to go along with his length. He's just not really explosive. I think he can potentially play minutes at 3 positions depending on match-ups.
If you go to 1:33 - 2:21 in this video, you can see what his athleticism looks like in an unstructured, pick-up setting. Again, he's not flying off the trampoline, but he's able to get where he wants to go. He's the guy in the blue USA shirt.