The way I see it, JPJ is like the product-improved Zack Frazier.
Frazier is your classic tape over traits guy... an athletically middling "power" style blocker who just does everything right. And I actually like seeing that, because center's a tape over traits kind of position. You don't need to be an overwhelming athlete to be successful, and Frazier does so many good things that will translate.
But let's put it this way. JPJ's a power guy too, he's got some outstanding film too, but he plays at an NT-esque 6'3" 328. In terms of size and strength, he's like the blocker equivalent of Vince Wilfork... but he still moves well enough to play pivot. It's a rare athletic combo, and when you pair it with unanimous All-American tape, you're pretty much looking at a unicorn.
I see JPJ as one of the best centers to come out of college in the past 10 years. Frazier's good, but he's just not in that same talent league.
Likewise... Barton is a pretty unique dude. He's more of a "mover" center, if you will, than a "power" center, but he moves at a unicorn type level. If you buy his Pro Day numbers, RAS ranks him as the most athletic college guard prospect ever. I'm not sure that I do buy that, but he's got to be north of the 95th percentile.
Great film, supreme athleticism... some teams are going to be drooling. Barton personally isn't my cup of tea, but he would probably be Kyle Shanahan's shot of whiskey. If you want to follow that, Frazier is more like a can of Coors. You'll just keep drinking them for 10 years and hardly notice it.