If Walter plays the type of defense that he showed in high school, then he could be comparable to a Kentavious Caldwell-Pope, which is a very valuable player archetype. Keep in mind, it took KCP several years to really become consistent. He was pretty middling in his early years in Detroit.
If Walter doesn't play defense like people think he's capable of, then he's more like a Buddy Hield-type shooter. Walter is considerably younger than Hield when Hield was drafted, but Walter hasn't shown that level of consistency.
This whole draft maybe eye-of-the-beholder, but I could see Walter slipping into the teens due to inconsistency. That's what happened with Keyonte last year.