Also note that if I put only the internal display in /usr/share/sddm/scripts/Xsetup, it still behaves the same displaying double-login on the login screen.
xrandr --output eDP-1-1 --auto --primary
Login screen isn't really a problem. What's more annoying are mouse boundary problems after I leave the computer for a while. I'm not exactly sure when that happens. If I close the TV off and on, it's fine. If I go back to lock screen, turn TV off and on, it's fine.
But if I leave the computer for a while... then the mouse stops being constrained to the lower-left corner, and there are also V-Sync issues when watching videos.
This; combined with the OpenCL problem, make for a very irritating experience right now.