I've towed many trailers, from utility to cargo to popup to TT, for a total of perhaps 200,000 miles. The thing that will bite you with sway is having too little weight on the hitch. If you have 10-15% of the trailer's weight on the hitch, sway is mighty unlikely with a TT of the size you're contemplating.
I tow 16' to 17' with my Highlander all the time. Wheelbase is shorter than your Ridgeline's. No sway whatsoever, and handling has been great. You should not need any sway control. I did buy and use an Andersen hitch during last summer's travels, just because I wanted to improve the ride (reduce front-to-rear bouncing).
Now, one time I had a scary sway problem with a 4x8 utility trailer! I was young and ignorant then, and had loaded it with a steel structural part that stuck out the rear and gave the trailer a negative tongue weight. So it can happen when you don't load correctly, like I did that time.
Unlike most folks, I have never felt that a tandem towed any better or bounced less than a single axle. I had a Rockwood 23' tandem and the drawers and doors would pop open constantly. My single axle 16' KZ doesn't have this problem. I had a tandem cargo 6x12 that seemed to bounce just the same as my single axle 6x12 (based on how it treated the contents). Of all the above, the one that felt unstable when towing was the Rockwood, so I used an Equal-i-zer WD/sway hitch with it and then it handled fine; I think the 23' length coupled with my 111" tug WB was the issue there.
Between 13' or 14' get the floor plan you like better (or can afford). I hope that helps.
