I use to split personal and work stuff.
Mostly just change desktop wallpaper, have different pinned apps, and have some apps forced to start on specific activity using kwin rules.
And I sometimes also on top of that use workspaces, for additional split if different set of work/personal activities like switching between projects or leaving chat on one and IDE on another.
So it's almost like a simple 2x2 workspace grid but with additional window/taskbar rules.