To be honest, I’m not sure about those files - but I’ve been scouring the forums these past few weeks looking to fix a graphic issue of my own. This post
https://forum.manjaro.org/t/plasma-desktop-acting-strange-on-reboot/53356
gave me some direction and sort solved 1 problem - but not everything as I have a 2 monitor setup using 2 identical graphic cards - though as I’m using an APU of yesteryear this also gives me a 3rd graphic output via my mainboard - all AMD radeon - unfortunately since switching to KDE recently both monitors are only willing to work on the one card - on the initial installation they worked on separate cards - after moving my pc a few weeks ago & then reconnecting I started having display issues - so wish me luck - I know the answer is somewhere in the forums & I do hope someone here can help you - my advice is to check out the wiki’s if you have the time or perhaps reboot on the installation usb for manjaro with both screens and make a note of relative config files.