GNOME is the best performing modern DE outside of lightweight nice DEs. KDE is by far the worst alongside Deepin. KDE is so crap, I had to turn off all the animations and compositor to bring CPU usage from 70 to 10-15%. This was a stock Debian 12 KDE setup on i5-7200U. GNOME in comparison idles at 1-2%, max 3%. XFCE and LXQt sit around 0.5-1%.
KDE is an absolute mess and is a hobbyist DE in comparison to the professional GNOME.