For RGIII, he has to transition from an entirely different way of playing the game and adapt his considerable talent to a style of play he has not only never mastered but has never really learned.
IF he can dedicate himself to learning to be different from the QB he has always been, accept his NFL coaches coaching and finally put behind him all the "He's fine, his mechanics are good" enabling he gets from Tedford and Bryles, then
maybe, maybe he gets his deep ball mojo back and his low turnover/sack ratio that he had back in college (look at his TD/INT ratio in college - it was insane. Yes, I know, it was a spread offense and, for the spread offense, QB's usually have very good TD/INT ratios). It is all on him - as others have said - to dedicate himself to the film room, listen to the coaches, and accept that he has to walk through an NFL offense before he run it. ---- If he can do all that, his ceiling - even in year four (the guy
just turned 25 in February!) - is simply much, much higher than Kirk's.
For KC, he has to figure out how to stop throwing picks. He needs to change something in how he views the field, works his progressions, or makes his decisions. My problem is that, unlike RGIII's flaws, I just don't know that there is anything that coaching can do to change KC's basic inability to consistently avoid picks. Sure, Gruden dumbed down the offense for KC but KC's constant turnovers completely stymied Gruden:
Jay Gruden Can't Explain Kirk Cousins' Interceptions
So, on one hand you have a QB currently incapable of running a pro offense and who has clearly identifiable flaws that may be fixable with solid coaching and a player dedicated to change - a trait the player has not readily demonstrated.
On the other, you have a QB who has a higher floor but is also deeply flawed. Further, it's not even clear that there is a path to fixing his flaws because he has been making the same mistakes throughout his collegiate and professional career and there is no clear, identifiable teaching/coaching point to correct them.
Quite frankly, as much as I truly hope Griffin can get it together and The Guy - I just don't know if he ever will be able to do so. As for KC, I just don't see him ever losing his knack for throwing untimely interceptions - it's just part of who he is.