Use openSUSE Tumbleweed. It's a rolling release distribution with the best a great KDE Plasma implementation.
Now, your specific question boils down to choosing between Arch and Fedora, since, arguably, Endeavour OS is actually Arch Linux. Now, as you're willing to use a Qt-based DE, specifically Plasma, I'd say none of your options are ideal. That's why I mentioned openSUSE Tumbleweed, but, for you, I'd say Arch Linux, however, you currently use Arch Linux, hence, you should just switch to the Plasma DE.