I think it would help with making Plasma more stable if there was an option to install Plasma Beta releases and a new ex. Alpha-version that updates to master every couple of weeks from the 'updates' settings. sort of like kdesrc-build without the build and with a GUI. or sort of like Windows Insider, but with the option to switch between stable and alpha at the login screen.
I think that's out of scope for KDE and a suggestion for the distro realm and not actionable.
Have a look at running your test systems as virtual machines. Check out KVM. You then have freedom to mix and match your systems and be sure that one does not corrupt/influence another. You also you get the options to do snapshots before changes to allow roll backs and to make complete backup copies of systems.