The point is that if you will not edit the fields on a site then the only thing you need is the JSON files. They only need to be synced to the DB if you need to edit them. I don’t generally worry about what version is being used because I have dev servers where I do all the modifications. The only exception to this is custom fields created for a specific site. I use parent/child themes as well. The field groups for the theme are in the parent. The field groups specific to the site are stored in the child theme’s acf-json folder.
