Latest video drivers/updates messed up my displays

Try setting all at 60Hz

mhwd is only a database and install scripts - so no changes are made to your system with those.

You tagged your topic with Plasma - custom theming the most common source when it comes to Plasma issues.

It is therefore highly recommended - even necessary - to revert all parts of your theming to default Plasma Breeze - including the sddm greeter theme - to avoid potential issues with the sync.