You may want to look into getting a tiling plugin for KDE. I'm in pretty much the same boat as you, used to use tiling WMs but now on Arch + KDE. The KWin tiling plugins are fairly simple - the only configuration is setting shortcuts to move windows around and resize them (I use super+WASD to move between workspaces, super+ctrl+WASD to move windows around on the screen, super+alt+WASD to move windows between workspaces, and super+Q/E to resize windows). That's it - the plugins make using the computer easier in 95% of cases without adding too much complexity, for for the other 5% you just toggle off the tiling and do it manually. And of course the mouse is still usable to move/resize windows.

Here's a newer script that overall seems to work better: https://github.com/lingtjien/Grid-Tiling-Kwin

And the older script I used to use: https://github.com/faho/kwin-tiling