Unless something changed recently, it is weird to say that GNOME/KDE is heavier/lighter when they are both insane resource hogs. I use Xfce or MATE nowadays.
Well, XFCE resource usage grew with GTK3, probably :(. But there's something off in their test methodology. They claim to measure idle RAM usage, and there's 2x difference between tests, on same distros..? (for comparison, my Arch XFCE install takes 480MiB after boot)
Plasma has made massive improvements especially around performance over the past couple of years. I switched from MATE myself and haven't looked back. I recommend giving it another look!
I'm appreciating the time-passing irony in suggesting MATE, given it is a fork of GNOME 2.x and that it had plenty of it's own share of "resource hog" complaints back in its day.
Plasma/KDE is mostly great, but a major thing that GNOME and Xfce still do better is GVFS and GVFS-FUSE. That means I can browse to smb://something or sftp://something, double click a file and it just works whatever the application is (e.g. play in VLC, edit in VS Code). This has never worked in KDE where only KDE apps can open remote files (and even that has bad performance).
GVFS/GIO is nice, but at least on LTS, it can be a bit rough (with i/o errors under load, at least during PhotoStructure imports). Also, somewhat frustratingly, the GIO system mounts network file systems with paths that include a colon character, which breaks standard PATH parsing.
I disagree. I started on Ubuntu 19.10 with GNOME but switched to sway because gnome-shell was always taking 3+% of CPU. It's hard to understand why something that should be doing nothing is one of the largest power draws on my laptop.
