Thank you, that makes perfect sense.
Now that that's bit's clear may I carry on with a related question. I would like to create a custom plugin that I can apply to new sites as I create them, essentially a settings page for generic site settings so that I don't need to recreate them for each site I build.
1) I take it metabox settings pages are a form of custom post type and therefore get saved in the posts table, but the options fields associated with them are saved in the options table?
2)very specifically oxygen related (and for oxygen 3.9 + where metabox integration is built in). Will metabox fields that I add to my custom plugin be visible under the metabox tab when selectiong dynamic content to be added to oxygen elements or would one need to use rwmb_get_value() to retrive data from those custom plugin metabox fields?
Many thanks