I struggled massively with performance, especially after like 30 minutes of playing and FSR didn't seem to do much, so I tried the amd_fidelityfx_dx12.dll from Stalker 2.
My FPS is now better and stable. So may be worth a shot for you if you are using FSR.

Replace amd_fidelityfx_dx12.dll in INSTALL LOCATION\OblivionRemastered\Binaries\Win64 (be sure to backup yours).