Importing options and how best to deal with two itunes libraries?

I’m importing my music to a new Nucleus with internal SSD, should I import the complete Itunes media folder or just the iTunes music folder and the XML file to include playlists?

Also when I use Itunes, I’m accessing the media files on an external hard disc attached to my mac and not the one Roon will use on the SSD, how do I update the music and XML file on the SSD from the Itunes library in the external hard disc on the Mac?