Even though Payton was a junior, he was extremely young. I don't even know how he did it..... but he was a 20yearold rookie!!!! Just for comparison, Skal was a 20yearold rookie for us too. So him being a junior doesn't matter all that much. It would be less than a year gap between Fox's and Paytons age. Payton isn't as quick as Fox, but they're very very similar players. Payton is the much better playmaker, but as you said, Fox is the better athlete. But to say Elf isn't athletic is incorrect. Fox is by far, the better prospect, but they are very similar.
Shot needs a ton of fixing. 25% really tells you a lot. Again, Wall was already the better shooter coming out of Kentucky. Fox attempted a low number of 3s, and had much lower % all around. Lots of recent prospects who can't shoot and have busted as PGs: MCW, Exum, Smart, Payton, Mudiay, and Dunn have all been disappointing. 3pt shooting is extremely important in the NBA. For Fox, it's the difference between being a franchise PG and being a backup PG.
I think people overplay Fox's passing ability. He's probably the 4th/5th best passing PG in this draft. I also wouldn't call his game patient. Lots of times where he erratically attacks the rim in attempt to draw fouls. I just don't see the appeal in a non-3pt shooting PG. He's a all dom. slashing PG. I'd rather the Kings draft other prospects who's games resembles the elite PGs. Curry, Westbrook, Harden, Paul, Lillard, Wall, etc.