Multiple concurrent desktop environments linux
Solution 1:
If you switch with Ctr+Alt+Fx you switch between sessions. E.g. you can easily open a pure text console. Any session can have it own window manager -- no problem. But they would always be 100% distinct, thus you would run different programs, different documents (or you will certainly run into ownership issues and conflicts), etc.
So, if you do very different kind of things in the different sessions this can be a good thing. Actually, I use this kind of setup: one session for normal work, another session just for online presentations. This avoids any kind of unwanted interferences during online sessions.