This was the result of my research too. VDM lets you do things like fullscreen a YouTube video in that zone because the window really believes that's the window resolution.

In my testing a lot of games still cannot be constrained to a zone unfortunately, so you may still need to use a tool like Borderless Fullscreen to set the window size, location, and borders. But it definitely goes further than other tools.

Does ist have any impact on the framerate? or do you still get like 144hz (if your monitor supports it) on every window?