[Discussion] How to achieve the best frame-pacing for dx9-11 games?

This is the only thing stopping me from gaming on linux. My goal is to run games at 1/3 the refresh rate of my screen (i.e. 40fps at 120hz) but achieving perfect frame pacing is impossible with a normal frame cap. I've heard of dxgi's sync interval option that mimics this but is it still relevant? To be particular, im using kwin/wayland and i've heard that on wayland, the compositor may override dxvk's sync behaviour for its own. Are these claims even true? And what if I run the game using xwayland? Is perfect framepacing at a fractional fps limit (like 40fps on 120hz) a myth on linux?

Also, my current setup on my windows machine is to use nvidia's 1/2 refresh sync (30fps on 60hz) with rtss cap at 30fps using the front-edge-sync cap method. This gives decent input latency with godly smoothness. Is it possible to achieve this on my linux machine at 40fps, 120hz?

Or must I resort to Gamescope, if that works at all? TIA!