Someone else mentioned it, but another vote for Aurora-dx (-dx for the developer version). It’ll give you the KDE experience without having to worry about your underlying system, leaving you time to work on software dev in a containerized environment of your choosing. Arch is great if you want to customize and tinker with everything, but given your parameters, I think not worrying about that bit will make your life easier as you focus on what’s more important to you. As long as you reboot your computer from time to time, you’ll always have the latest version and can rollback easily if something goes wrong.
And as is tradition with Linux, it’s not like you have to use whatever you decide forever. Distro hopping is a time-honored tradition!
Yeah, I thought the main devs were Latvian 🤔