Probably just remove the nvidia profile from mhwd …
to be double-sure you can make sure to remove anything in xorg.conf.d or mhwd.d
Then you may also wish to force-reinstall the video-linux profile in mhwd after the card is installed.
Yes … it is the preferred method, as opposed to using ‘amdgpu-pro’.
see this:
AMDGPU - ArchWiki
Also this:
Installing AMDGPU PRO by Archwiki - #6 by cscs