for a complete unisntall you should just be able to run sudo pacman -Rns <package_name> or yay -Rns <package_name> depending on how it is installed.
since you’re doing a complete unsinstall and reinstall, you should be able to just run sudo pacman -Syu <package_name> or yay -Syu <package_name> and it will completely reinstall. If you are worried you have a corrupted download of the file, clear your package cache completely and run those commands, it should download a clean program install file and reinstall.
I’m not familiar with Mangohud and Goverlay, so unfortunately can not help our further, but maybe one of our other community members can.
this is one of those questions better asked in debian forums if they still haven’t released it