Generally, when building a plugin I keep the fields in the admin of ACF and turn on local JSON for the theme I using during dev https://www.advancedcustomfields.com/resources/local-json/.
Once the plugin is complete I make a decision on whether to put the files into a local json folder inside the plugin and add a load point or to move the field groups into php https://www.advancedcustomfields.com/resources/register-fields-via-php/. This depends on whether or not I want to make the fields’ labels and values available for translation.
