So I'm likely having a bit of a derp/forgetful moment here. I'm running Windows 10 with an RTX 2060 and I can't remember how to get games to scale individually. I can find my way to the Nvidia Control Panel and "Adjust desktop size and position" and from there I can tell it to select "No Scaling" and to perform scaling on the GPU. That lets me run games without them stretching to the full window size.

However its a blanket setting for all games and some games just don't stretch as well as others. So how do you set it for each individual game so that I can pick and choose. Especially since the GeForce Experience panel is very fussy now and only likes to list certain games that it supports (which means a lot of older titles that don't need "optimising" aren't listed - unless I'm using that wrong).

I think the setting simply is a global one for nVidia drivers. All I normally do is leave it on "Aspect ratio scaling", "Perform scaling on GPU" and tick "Override the scaling mode set by games and programs". Everything is then fullscreen but without being distorted. If you want centered 1:1 (no scaling) in some games but not others, then I think you will have to toggle it on / off like that.

Edit: You could always create a post on the nVidia forums suggesting per-game scaling mode be added as a feature? Enough people wanted the Integer Scaling option that they added that, so it's worth a try.

The closest I've ever had to "per game" is to disable the scaling altogether and then use the different settings on my TV to scale or not scale.