I want a QB who is smart and a total football junkie, first and foremost. The ability to learn an offense, as well as the coaches know it, and be able to diagnose how a defense is attacking your offense (overall strategy and play to play) is crucial, along with processing that information very quickly is paramount for me. Making good decisions consistently will allow a QB with lesser arm talent to keep the starting job and win games. Happy feet make me nervous. That's a sign of indecisiveness. P Manning is one of the few QBs I've seen succeed with happy feet, and succeed he did.
Number 2 on my list is accuracy. It doesn't matter how strong your arm is if there's no real idea where the ball is going to go. You can get away with less accuracy in college, not so much in the NFL. 2b would be vision/anticipation. Can a QB see the whole field and see a WR coming open/throw him open? That's pretty dang important in the NFL where an open receiver doesn't even resemble a cousin to an open receiver in college.
How does a QB handle pressure and big moments? Are they winners or do they wilt? I guess I would label this intangibles. Do they rise to the occasion or crash and burn? My biggest question with Kizer.
Arm strength comes next. Can the QB drive the ball and make all the throws? Being able to drive the ball on intermediate and deep outs greatly affects play calling. This is where velocity comes into play. Windows are usually tight and velocity and accuracy are crucial.
That's how I judge QB prospects. Thankfully, there are a ton of youtube videos that show every throw from a game and not just highlights. You gotta see the bad with the good.