@Evil_Mantis14 There's nothing obvious in your dxdiag, and since your graphics driver is a few months old, I doubt this is just about the driver, or you would have noticed it before. (I'm not suggesting you need to update the driver, at least not at this point, just observing.)
If you happen to be using any filters through Nvidia Freestyle, please disable them; you can open the options with alt-F3.
If that doesn't help or isn't relevant, please try playing in a clean boot:
https://www.windowscentral.com/how-clean-boot-windows-10
When you reboot, please also go through the Task Manager's background processes list and disable anything that isn't critical. For example, the Corsair software may still be running (even though that goes against what a clean boot is for), but you don't absolutely need it for this test. Anything you shut down will restart the next time you reboot.
If that doesn't make a difference either, please take some side-by-side screenshots of a sim in CAS, in both fullscreen and windowed fullscreen. It would help if you used one of the premade sims, so I can compare with my own game, but if not, just widen the shot enough that I can see what skins and items you're using. Please use base game items(not from packs), just to keep things simple.