How to setup i3 and xfce together? How to setup i3 and xfce together using lightdm?

Question

linux

At first I used only Unity, then I switched to i3wm. Now I added xfce, but demolished Unity. I can not set up a screen to switch between wm.
I think in order to set up two wm on one system, you need to delve into the structure of the system itself with the Linux kernel. How it starts and so on .. [sometime]
Edited the question, for the reason that I did not know how to ask what I want - How and what dm to use in order to load different wm?
I tried to start startxfce4 instead of ligthdm(startx), but without superuser rights it doesn't start, and if it starts (chown 777), then everything is exactly under root. No screen to select login user - login automatically as root:

How to run startxfce as non-root user?
xfce is a graphical environment with a desktop
startxfce4 is what launches xfce (its own startx for xfce)
Or, having several window managers (i3 and xfce) on the system, can these graphical systems work? I know you need to use lightdm or any other dm(xdm) in order to set up i3wm and xcfe together. The question is how to do it? How do you do it?

Answer 1

xfce is a graphical desktop environment
startxfce4 is what starts it
you need to use lightdm or any other dm(xdm) to set up i3wm and xcfe together