The spread offense isn't primarily run in the NFL during the regular season, although this past Super Bowl has illustrated it's effectiveness in a must-win situation at the pro level. During the regular season, RGIII got hurt, Kaepernick threw from the pocket, and Braxton Miller played college ball.
RGIII got hurt, then they tried implementing him more in the pocket, and Washington struggled mightily to move the ball without RGIII as a threat with his legs. Kaepernick is straight power spread. Kaepernick executes the pistol offense with heavy elements of zone read. San Fran also moves the pocket for Kap a ton, so saying he throws from the pocket primarily isn't the whole truth. Braxton Miller was an example most people can conceptualize being on an Ohio sports board. But elements of Ohio States current system under Tom Herman/Urban Meyer are definitely becoming very commonplace in the NFL. As you mentioned, Seattle moves Russell Wilson a ton as well, with elements of spread offense.
Correction, we don't see the old power run game in the college game anymore because the college game is exclusively spread, while the pro game borrows elements and weaves it into the pro style offense. The pros run a hybrid, hence your examples of Peyton Manning, Tom Brady, and Drew Brees. What is most important with Manning, Brady, and Brees is clearly not their mobility.
I think its disingenuous to say Denver, New Orleans, and New England don't run a spread offense. Each team operates almost exclusively from 3+ WR sets when taking split TE's into account. None of them feature a power run game. All of those teams are operating spread based offenses. It's no secret Chip Kelly spent several straight off-seasons in New England with the Patriots staff teaching them elements of his offense pre-NFL job jump. Denver's OC is considered a "spread guru". And New Orleans is a quintessential spread offense.
The bolded section, again, show that you aren't talking about the pro game as much as the high school and college games. In the pro game, running the college spread plays exclusively lead to too many hits on your QB. Oakland recently tried to run college plays with Terrelle Pryor and clearly there were problems. Namely, the few choices of receivers are easily covered and the QB ends up hurt.
To most peoples surprise, Terrelle Pryor is much more comfortable in a Pro-Style offense. For all of Terrelle's natural ability, he hates contact and is not a north-south runner. He went to Ohio State over Michigan (Rich Rodriguez) and Oregon (Chip Kelly) because he wanted to learn in a more pro-style system (Jim Tressel). For all of Terrelle's broken play scrambles, the guy was pretty awful on designed QB runs. Just not natural for him. And Oakland didn't really run "college plays" for him once he took the starting reigns. They tried developing a special package for him when Palmer was the starter but it was a brutal plan. Once Terrelle took over starting duties he looked decent under Olsen until his OL fell to shambles and he had one of the worst receiving cores in football to throw too. It was just an awful situation for Pryor to succeed. The Seahawks in probably the best thing that could happen to him.
I'm short on time, but if Manziel's legs and escapability were on Hoyer's experienced brain and height, we would be having a different conversation.
I like Hoyer and the things he showed last year. I like that he has a quick trigger and has shown good leadership qualities. I'm just hopeful Manziel is able to carry some of his magic from A&M to the NFL. Will he? It's tough to say. I like his escapability, I like his frame in terms of taking hits (he's compact and has shown an ability to avoid huge hits), and I like his guts on the field. A lot of that can get him in huge trouble in the NFL, but with some experience and a solid run game, I think he could be pretty good. We'll see....
In the meantime, I'll support whoever is under center, and hope the Browns can compete in a very mediocre AFC North.