I haven't tried xfce in several years. Has it gotten better since then? Gnome
shell is very fast on my computer so no need for a lighter DE. The only thing
that slows down gnome shell is having abrowser or icecat with many tabs open.
Currently I am trying suspend tab to see if unloading tabs not recently used
will get back the performance of my pc working fast again.
Suspend Tab
https://addons.mozilla.org/en-US/firefox/addon/suspend-tab/
Suspend Tab licenses
https://addons.mozilla.org/en-US/firefox/addon/suspend-tab/license/1.0.2016020401