If their computer can handle running a windows vm on virtualbox, I’d recommend that over dual boot. Windows update will almost certainly cause issues on boot…eventually.
Jump into Linux with both feet. Use the vm as a crutch or a bridge to windows only software.
Follow the advice below… backup everything. If you have a 2nd hd, this makes it easier to keep files and is separated.
If you’re prepared to reinstall, it’s easy to nuke it and try again. It’s part of learning and sometimes easier to troubleshoot.
Why the pain of Arch? You probably fell in love with the rolling release, wiki, and the AUR.