They are self-standing themes (however if a client need some customization I would implement that via a child theme).
My aim is to have a core ACF setup that I can tweak if a theme requires it. Right now I have used the admin UI to register the field groups. Ideally ACF would have a native “If current theme is xxxxxxx” location rule.
Eventually the fields will be deployed on the sub-sites of a multisite network which I hope will not add too many constraints (had to start this project somewhere and it wasn’t there).
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