120Hz works out of the box on the latest version of Parallels (20), but on Linux VMs they default on 60 whether you install one via an ISO or with an automatic installer. I found this post and all these commands work except for the last one, though it seems to be for X11:

$ cvt 4112 2572 120  
$ xrandr --newmode (everything after "Modeline" from above command)  
$ xrandr --addmode Virtual-1 4112x2572\_120.00  
$ xrandr --output Virtual-1 --mode 4112x2572\_120.00

There’s no option for KDE X11 in the login screen, just wayland. I looked up the kscreen-doctor command but there isn’t a lot of documentation on it. kscreen-doctor --outputs only shows 60hz options, I wonder if I could add a 120hz refresh rate option with it and get it that way.