Before you do any of this, make a backup. It's much easier to restore one and start over then to try to "undo" some of these things.

Merging in the video and process I explained will permanently merge them, leaving you with only the big field. Can I ask why you want both options? One of them will contain all the data and the other one will just be a boundary most likely. It sounds like you're trying to make a complicated situation even more complicated. (that's just me)