If you keep all your personal files in your home directory and stay away from snaps and don’t switch desktop environments, i.e. stay with GNOME or KDE you can switch back and forth as you wish. There are minor “bugs”/issues when switching between DEs but nothing too serious. Best is to have a seperate drive for Home but that’s luxury. Choose one (bigger) distro. If you need to install another distro because a package is only available on that system, just use distrobox instead. Want to check out another distro? Use a vm. Don’t use a nieche distro as a beginner. Use a system that auto updates itself so that you will never interact with the system again.