I have little time to play games these days, but I do that. Have two machines, both always on, one of them a windows one for games, the other runs linux for everything else. I use a usb switch to, on-the-fly, change all the relevant devices (mouse, keyboard, headphone dac/amp, etc) and adjust the monitor input to use one or the other. It works extremely well, and takes ~1-2 seconds to switch.