New and with a lot of questions
I have no relevant experience here, but may I suggest a reason why the tow behind might be less practical than you think? I think it's a great concept, BTW, don't get me wrong.
Apart from the issues of having it slow you, not knowing if it separated from you at some point, or where, and having it bumping against you, complicating mooring and slip usage, etc., there's this:
What would you store in it?
Given that you'd likely need to be stationary to access the storage, have to board(?) the "trailer", unlock and open what I hope is a watertight portal, get whatever it is out, transfer it to the main vessel, re-secure the trailer, and re-board the boat You now have something on board that you must have room for, but presumably didn't have room for before you did all that, which was why it was in storage in the first place.
My guess is that after going through that about twice, I'd come to some real conclusions about what's in the trailer that I can't live without.