Hello disaster mong!
I am using Tumbleweed / KDE since August 2016. My experience is quite different, even with the oldest and smallest machine: “I like its snappiness.”
Presumably you did some tinkering. Try a pristine system first, e.g. https://download.opensuse.org/tumbleweed/iso/openSUSE-Tumbleweed-KDE-Live-x86_64-Current.iso.