Brown is 6’7” with 6'11.75” wingspan. And I think he is significantly more athletic. That said I see more Cade Cunningham .According to the Internet Harper is 6'6 with a 6'10 wingspan which puts him about the same size as Jaylen Brown, just with a 2 inch shorter wingspan.
An elite primary scorer at that size can definitely win you a championship as the best player.
https://www.nbadraft.net/players/jaylen-brown/
