I think I've read somewhere that FSR3 has trouble when there is a too low base of "real" frames it has to work with. So don't expect it to do miracles in every scenario.
Hopefully something like this can be included in a future version of Wine/Proton/Proton-GE. Proton-GE doesn't have an issue page. I think one would have to reach out via Discord. I don't use Discord though.