Question about FSR 2.0 in serveral games

I am tinkering around with FSR on some games like Borderlands 3 and Doom Eternal.

I use Proton-GE 7.43 at the moment and I set the necessary launch options like ENABLE_VKBASALT=1 WINE_FULLSCREEN_FSR=1 WINE_FULLSCREEN_FSR_MODE=ultra

Vkbasalt isn't necessary I know but without the image gets quite blurry. WINE_FULLSCREEN_FSR_STRENGTH doesn't do anything no matter what value I set.

So I have a 1440p display and set the resolution to 1970x1108 which should be the resolution for FSR in ultra quality mode.

When I set it everything looks like that's the resolution I get put out on my display. HUD's getting bigger, everything is a bit blurry and you can clearly see some strange artifacts since 1970x1108 is no integer divider for 2560x1440.

My specs: R9 3900X 32GB RAM RX 5700 XT

EndeavourOS, Kernel 6.1.2 Mesa 22.3.2 Proton-GE 7.43

I don't know if that is normal behavior or not but ai can't imagine it should be. In all those comparisons on the internet you can hardly see the difference between native resolution and FSR 2.0 ultra quality. I see it quite clearly especially since everything gets bigger like it should when lowering the resolution.

So what am I doing wrong here? Is it wrong to set the resolution to 1970x1108 in the game? Does FSR already work by just setting those launch options?