kwin_wayland
supports launching Wayland displays inside a Wayland display. This can be used to launch KDE Plasma inside these windowed displays, and that recursive.
A GitHub with the script is here.
If you want to test Plasma, I think doing it in Distrobox would be a good idea, so your configs and Co are protected from corruption.. The KDE wiki gives instructions for that.
If you're trying out mobile or bigscreen, sure, that's an option.
If I'm trying to get bigscreen to work, and I need to make code changes to do so, a window is better.