This doesn’t really have a positive effect when using vorpX. vorpX already supersamples the final image that is sent to the headset. Adding an additional multiplier on top of that only has a small effect on image quality (if at all), and depending on the factor chosen leads to excessively large final eye render textures (up to 6000×8000 per eye).
What does have a profound effect on image quality is running games at a higher resolution. The default suggestion of 1280×1024 is a compromise between quality and performance. 1920×1440 would roughly result in the same quality as native apps, resolutions above that would be supersampled resolutions.
Just keep an eye on performance when changing the game resolution (ALT+F), 45fps+ (game) should be maintained for a comfortable experience.