Edit: this is the latency project I was thinking about https://danluu.com/input-lag/
If you put a bit of load on the modern hardware things get dramatically worse. As if there is some excuse for it.
I had this thought long ago that the picture on the monitor could be stitched together from many different sources. You would have a box some place on the screen with an application or widget rendered in it by physically isolated hardware. An input area needs a font and a color scheme. The text should still be send to the central processor and/or to the active process but it can be send to the display stitcher simultaneously.
You could even type a text and have it encrypted without the rest of the computer learning what the words say.
I look at and click around KolibriOS one time, everything is so responsive it made me slightly angry.