Sorry for the slow reply. I have not been on here for a few weeks.
I am flat towing a 2016 ND Miata. I have the Roadmaster baseplate, Blue Ox towbar, and Stay in Play brake controller. I installed all of that myself. I got tripped up on the lights and ran out of time so I had a hitch shop fix the lights for $300.
I researched a lot before towing the ND and the conclusion I found was that you need to leave the car in neutral and idling while towing to avoid burning up the transmission (6 speed manual). I’m not thrilled about this but I have pulled it over 3,000 miles this past month with no issues. The good news is the mileage pegs out at 99.9 mpg while idle towing.