What is the best way to move a folder of photos with their respective *.DOP and *.XMP files?

Moving folders outside of PhotoLab disconnects PhotoLab’s database from the moved files.
Star ratings are stored in .dop and .xmp sidecars, but history is exclusively stored in DPL’s database. Beware: Synchronising star ratings does not work under all circumstances. This has been covered in a few posts already, e.g. here: Star Rating not working in PhotoLab 5 for dop files (without using PL database)

DPL 5 does not support folder moving on macOS, but you can move or copy (group of) files from one folder to another - if the target folder can be seen in DPL’s sidebar. Beware: DPL is picky about where you can move/copy files to. Test your ideas before seriously committing your originals!