I don't love Bo Nix. But the reality is that the Broncos spent a first round pick on him and have 5 years of team control.
Zach Wilson they spent the equivalent of a late 6th/early 7th and have one year of team control. So Zach will almost certainly be behind Nix.
The real question is QB2 or QB3.... And that depends as much on what the Broncos want as it does on Stidham vs Zach. Zach absolutely has more upside, better physical gifts, more wow plays. But Stidham is more stable and reliable.
I could see them opting for Stidham as QB2 just because that's what they want in a backup, not because he's actually better