As to Quinn Ewers: He dealt with a lot of pressure at Texas. Everyone wanted to see Arch Manning. Fans, announcers, pundits, experts. Of course we saw what happened when Arch finally did play, and it explained why Ewers started for Texas all last season. Quinn remained poised very well through it all. Also, Ewers fall in the draft was surprising. His fall was overshadowed by Sanders fall. So people forgot about him. But he did well in college, and the potential is there.
Here's the problem with Tua. The way his contract was written, the 2026 season is where it's most heavily loaded, with $54m guaranteed. They can't easily cut him, or it would cause something like a $57m dead money hit, which would be brutal, as Miami is currently -$5m over the cap for next season. Or they could split it at $99m in dead cap hit over two years. The only other option is to find a trading partner. Someone with some cash, who would take Tua and a draft pick for junk in return, then keep Tua as a backup for a year or so, then just cut him. But even that seems unlikely as few teams have that cash, or want to spend it that way (Jets? Titans? Raiders? That's about it).
Good article on ESPN explains the details. In it some exec suggested the Fins just rip off the bandaid and cut him, the way Payton did with Russell Wilson. If that happens, I can see Tua retiring. He has plenty of money, and health concerns.