I highly recommend Hyprland if you want a truly infinitely customizable UI. But, there’s a big learning curve to even using it, let alone installing it and setting it up.
You could use endeavourOS as your operating system, which is Arch based yet easy to install. I can’t speak to setting up Hyprland on other distros as I haven’t done it, but I’m sure if you look around you’ll find out what you need to know.
Install your software from official repositories and flatpak and you shouldnt have any issues. My latest install has been going strong for about 6 months without issue. Linux in general is quite stable unless you’re mucking about with things you don’t understand, and if you do like to live dangerously in that regard, it’s a great way to learn a lot.
If you’re worried about stability, keep good backups. Back up your important personal files, as well as your config files so you can reapply any customizations you had in place.
If anything happens that’s too tedious to troubleshoot, reinstall, it takes like 20 minutes tops and gets you back to square one.
You could also use time shift to create system snapshots.