Truthfully, I think the answer is somewhere in the middle. I do think it's a fairly difficult scheme (essentially a dumbed down NFL scheme), but I also think Max just is not a natural at safety. Ridiculously good athlete, overall, but just doesn't see the whole field and the chest pieces moving on the board like a FS needs to in a defense that relies on post-snap rotation.
As for Studstill, if he plays a lot this year, I'm not expecting the world from him, I'd just like to see slight improvement every week. I do believe Brian Kelly when he says Devin picks things up naturally though. He was one of the most impressive DB's I saw on film last year. It's not because he's an athletic specimen of because he's uber athletic, but rather, because he has elite recognition and reaction skills. His film showed a guy that would read, diagnose and take decisive action... And best of all, finish.
Some kids are just football players.... Look at Josh Adams, another 3 star guy like Studstill. He's lanky, 6'2, 215lb athlete you expect to lineup as the reiceiver into the boundary, who runs ok, but relies on his strength as a possession guy... Then the game starts and he's the tailback in 99% shotgun sets, running inside zone with good pad level and patience, and although he probably isn't a 4.4 guy, people don't seem to catch him when he's out in front of them... He seems to be as fast as he needs to be.
I think Studstill is a lot like Adams in that regard. He's just made to play football...
I still feel the best thing for this defense would be to move Redfield to SS, where he can be physical and an explosive athlete in the box, with far fewer coverage responsibilities. He excels at playing downhill, Dwyer than deep on the hash or in centerfield (both he and shumate were pretty sure tacklers last year), that wasn't the problem. Coverage was.
If it were my defense (which obviously it isn't) I'd set the secondary up like...
CB: Cole Luke
2. Shaun Crawford
FS: Devin Studstill
2. Jalen Elliot
SS: Max Redfield
2. Avery Sebastien
CB: Nick Watkins
2. Devin Butler
BN: Drew Tranquil
2. Avery Sebastien
LN: Shaun Crawford
2. Nick Coleman
Note: I'd move Tranquil to SAM backer to work with Onwualu and I'd also have him be my Big Nickel as the hang defender against the loss of Navy and the teams that like to spread you out and run it at you, such as Texas in game 1.