According to my tests the app seems to provide headless macs with a HiDPI virtual display with customizable resolution (tested via Screen Sharing, resolution switch on the fly worked, all resolutions are available without any real display connected - should work with VNC as well, but I did not test that).

I tested this as part of testing the app on Intel and Big Sur (BetterDummy worked fine on this Intel config with an integrated Intel UHD630 so headless Mac Mini 2018 users should be fine).