The real killer feature? Apple killed sub-pixel text rendering in modern macOS, making text look terrible on standard 1080p or 1440p monitors. RDM forces the GPU to render at a higher resolution and downscale it, effectively tricking macOS into giving you sharper fonts on cheap screens.
If you are using a Mac mini with a 1440p gaming monitor, or a MacBook Pro with an ultrawide 4K panel, It is the missing System Preference panel. rdm mac download
: If you encounter a "developer cannot be verified" warning, you may need to run sudo xattr -rd com.apple.quarantine /Applications/[AppName].app in Terminal. The real killer feature