Few years ago I had similar issues with a specific motherboard when using Win 10, Win 7 was fine.
I tried changing everything else besides the motherboard itself (CPU, RAM, GPU, Fresh OS install, drivers, BIOS etc.), only going back to Win 7 fixed it.
First few minutes were fine with the occasional FPS drop, but 10-15 min in it usually started dropping to single digits now and then, with 30min+ completely unplayable.
So I'd start with trying the steam version of the game, does it work there or not?
Then ofcourse the usual issue finding:
- Temps? Other resource usage oddities?
- Fresh install of base game + FAF (also deletion of gamedata folder and make sure no mods)
- BIOS update?
- Any other applications with similar issues?
- Fresh OS
- after this mostly hardware debugging/incompatibility debugging left
Just a matter of narrowing it down one by one by eliminating possible problem sources.