[Karellen]

Does Kodi have a preferred format for songs with several artist credits,

Yes, the default separators are shown in Item 8-14 here... https://kodi.wiki/view/Advancedsettings....siclibrary

You can add or remove items by copying that section to your advancedsettings.xml file then adding or removing entries.

I didn't know about MusicBrainz Picard, but an automated way to clean up the tags would be awesome !

Here is the wiki section on it. Links to the software (free) are at the bottom... https://kodi.wiki/view/Music_tagging#MusicBrainz

Just make sure you select the correct album when using it. Some albums have multiple releases that look the same, until you realise that the song order is slightly different, or the bonus songs are missing, or there is no disk 2, etc.