As we had this very same discussion on the forum of the other sim and I see it's still going here and people are still investing time in investigating and theorizing, I'll just leave this here as well as food for thought:
The "stereo" section of the nVidia profile was introduced many years ago, before current VR, and was meant to apply to monitors, either by causing anaglyph rendering:
https://3dvision-blog.com/wp-content/uploads/2009/06/burnout-paradise-anaglyph.jpg
Or nVidia's proprietary 3D Vision mode for their shuttered glasses which also required a custom monitor panel (or so I understand as I never got in to that tech):
https://techreport.com/r.x/geforce-3d-vision/stereo-shot.jpg
Ergo: any changes it introduces to the game's rendering should be immediately visible in normal screen mode, as they added these features long before VR was around and their purpose was to make changes to the rendering process of the game at the GPU driver level - all of which occurs before it is transferred to the HMD or your monitor. Therefore you do not need a VR headset to see the effects rendered, regardless if they look like a mess as in the screenshots above or if they are subtle and only visible when the scene is in motion they should absolutely be visible in 2D/screen/pancake mode as well. After all that's their intended medium and that's what happens when you modify rendering settings at the driver level. Furthermore, AFAIK they are not a post-processing effect either, so they should absolutely be capturable in simple screenshots (but even if they were there are tools to capture screenshots with post-processing effects in them as well [for example, the openvr_api.dll mod by fholger has a screenshot function which captures the final result, post processing included, right before it is outputted to your HMD]).
Example: you can completely disable anisotropic filtering and drop the quality of your texture filtering to the lowest possible and it will be immediately visible both on screen and in the image sent to your HMD because it is done at the GPU driver level, the exact same thing applies to any effect the settings from the stereo section would trigger.
Happy hunting!
