Hello @th3t4x,
Welcome to the Fedora discussion forum. /usr is not writable on SB so I don’t think you are writing to that directory unless you have made your system directories writable with rpm-ostree usroverlay to make it transient. If you are wanting to use Xorg, then just use the option for your login to select Gnome on Xorg. If you are wanting KDE you could then look at the Kionite spin Kinoite, a KDE (and now XFCE) version of Fedora Silverblue - #187 by decathorpe.