Can't tell you about footwork and technique.
All I know is that the guy thrives under pressure. He indeed is accurate. He can throw well on the move. Throws well from the pocket. Clearly his guys respond to him. All he does is win.
Like all QBs, he needs to go to a team that will develop him and build their offensive systems around his positives and strengths and not try to pound him into a mold or make him adapt to the HC's vision of NFL offensive football.
Yes, he's got to mature a little bit, but he's a college kid for Pete's sake. He gets emotional at times and goes a bit overboard. But Johnny Manziel he's not; this kid loves football. Height? Yeah, it matters to a degree. But both Brees and Wilson prove that you don't have to be 6'3" to be a great and successful passer in this league.
The QB needy team that passes on Mayfield is going to be sorry. Felt the same way about Prescott and about threw up when Dallas drafted him.
I can't evaluate all the intricacies of playing QB; but I know a strong and accurate arm, leadership, and instinctive play when I see it.
I'd draft him before any other draft eligible QB including Rosen or Darnold.