This is what I run in both my main gaming rig (I9/4080) and my retro rig (old i5 and Radeon 580) works great for both. Steam and Proton do 95% of the work with no issues.

Denuvo?

“Trade in” like theres a dealership willing to give you some kind of fair value for your old computer. That said, if you’re willing to be extorted by Microsoft, then you get what you have coming to you.