My PC isnt the best (3rd Gen i7 / 16Gb DDR3 / 1050Ti etc), but I never had a problem until Proton UI came into being.
I run 2x clients, both in potato mode, and I find when using the UI, the mouseover (and subsequent detecting of clicks / drags), is slightly delayed, sometimes resulting in missclicks, orbiting instead of jumping or dragging the wrong names into intel.
Due to my PC being such a toaster, does anyone know of any hints or tips which would reduce this lag? Im already using AfterBurner to get the most out of my GPU (overclocked).
What you are describing is exactly what photonUI fixed from me over the old UI. I doubt your graphics settings or any overclocking are related to that type of bugginess unless your CPU is saturated.
Did you install the nvidia drivers from a few days ago? they introduced a bug in recent version that caused high cpu usafe by nvidiaDisplay.container.exe