AMD admits that switching from spatial to temporal upscaling can be a bit more taxing on the GPUs, but the new FSR 2.0 upscaler should work even on Nvidia's GTX 16-series with good results. Team Red also reveals that FSR 2.0 implementation is fastest on games that already include DLSS 2.0 support.
https://www.notebookcheck.net/AMD-releases-additional-FidelityFX-Super-Resolution-2-0-details-at-GDC.609764.0.html