I'm going to push back a bit on the JJ McCarthy comment. Harbaugh absolutely runs an NFL style offense and JJ made plenty of NFL reads and difficult throws.
Now, what can be questioned is that because Michigan had such a dominating rushing offense AND a dominating defense, very rarely did JJ have to throw 30+ times to win the game and make those kinds of throws day in and day out. So, he has done them, just not at the frequency that many would like.
Also need to keep in mind JJ is the youngest of all the QB's coming out this year (just turned 21). He is best suited for going to a team that would sit him a year (like Mahomes did and no this isn't a Mahomes comparison) or a team that has a dominate running game/Oline, so he can be brought along slower.
He was one of the top QB's in all of college football in completion %, 3rd Down Conversions, 3rd down yards per attempt, and TD to INT ratio. Yes, he didn't have the number of attempts that others had, but he also didn't have to because of their defense and rushing attack. Plus, if you are an intangibles guy, JJ has that in spades (Coaches love him, Teammates love him, always positive, Team first attitude, etc).