SpaceInvaderOne is indeed fantastic, and his videos are done of the very best UnRAID documentation around. He also wrote the macinabox docker.
I've used Macinabox quite a bit... Actually I've used OSX on UnRAID quite a bit. I've used Macinabox just twice, as it's simply an installer. Once OSX is installed it's like any other VM.
Why do you want 60fps at 4K? If to watch videos, you're better off with Plex, if gaming you're better off with steam link / shield etc. There are lots of apps to let you remote in - VNC, TeamViewer, Google Chrome, Log Me In, Apple Remote Desktop, etc etc - anything made to log you into a Mac, but they don't tend to specifically target high framerates as far as I know