Trying to understand on what you are trying to say here. So you do mean you would like to mine monero without affecting your current works on PC or do mine when idle? as far as i know you can
do mine without maximizing the full usage of your own PC usage if you do tend to make use of minergrate on mining XMR. Unless if you maximize it to the peak then i would say
you can barely use it and talking with that kitty screensaver theres no such setting for it to be automatically launch when idle.

Correct me if im wrong.