vorpX has FSR built in since the last version, implemented in the ideal fashion directly into vorpX’s existing image processing pipeline instead of just slapping pre-built shaders on the final output. Adding a very similar second solution for doing essentially the same thing may happen in the future, but at this point is not a priority.
I just played around with this in a native VR title (FO4VR), since I was already using the FSR version in that game. NIS had slightly higher overhead and was slightly less sharp in that test. Overall I preferred FSR in that title.