How trying two use monitors?? As cloned screens
OR separate outputs (screens output, panels ect)
If cloned output, only need to say use in setting>display (can set different resolutions)
if separate outputs per screen a little harder

.
easiest to install arandr package to set where to use screen outputs (right-left/above-below ect).
Then you can set different wallpapers per monitor (SETTINGS>DESKTOP). Can set panels to different outputs (settings>panel) Set where windows will display (setting>window manager and settings.widow manager tweaks).
The virtual workspaces and pager seems to be global in xfce4

, but you can drag windows between monitors (if pager properties set to wrapping per viewports in (but switching window to virtual desktop works using 'window Button' right click menu
P.S. haven't really done this (my 2nd monitor (larger LCD TV), and my Laptop/tablet is connected to port-dock with internal screen turned of (can't see, it's in desk anyways).
SO maybe able to play with setting to get way like
J.Jay
P.S. I believe if you have XFCE installed over a Gnome ISO you can (mostly) *use their GUI's when in XFCE session*, and settings will save to the XFCE session

. But nautilus and other Gnome components may cause trouble (plus you well use a little more resources/memory.