Xerxes
I think he is referring to how to set the custom resolution to "EXCLUSIVE FULL SCREEN" and not to "window mode", as full screen exclusive does not have input lag and interference from the windows window manager".
Exactly like in the videos below, where I show the games that allow modifying the configuration file to put a custom resolution in full screen exclusive.
In my case it is 640x400 (CRT MONITOR IN 162HZ).
https://www.youtube.com/watch?v=5SnbrzvBZEY
https://www.youtube.com/watch?v=G3uA4j-5ys4&t=272s
https://www.youtube.com/watch?v=m-1TSFV2GUY
https://www.youtube.com/watch?v=l2Kw3T_IZzI&t=8s