I just don't see a starting level QB with Nix.
QB is getting to be more and more of a tools position, where being big, fast, and rocket-armed can overcome a lot of deficits. And Nix looks pretty athletically average by NFL standards. He clears the threshold for sure, but is he even as physically talented as 2023 Dak? Probably right in there, and Dak is one of the most "pocket" QBs left in the league.
Nix's volume stats are pretty much empty calories where the receivers do the work. His accuracy looks shaky and he doesn't deal with pressure well (or often, because Oregon gets the ball out so fast).
I can see a best case scenario where Nix ends up being like a Dak, but Dak put in a metric ton of work to improve to where he's at, and we're still asking ourselves if he's the guy. The more likely case is Nix ends up more like a Sam Howell or a Josh Dobbs. Kind of an aggressive gamer without enough physical tools to really game.
I think you take him in the 1st round anyway. This is a league where Daniel Jones makes $40M a season, so Nix will save you a franchise-changing amount of cap room over 4 years if he even turns out to be OK. At some point, you just bet that I'm dumb and wrong and take that plunge. I hated Will Levis last year, but he totally made sense in the 2nd, and he didn't look half bad this season either.