My 2008 Highlander has 170k miles on the odometer, and 140k of those are towing miles. I tow a cargo trailer for work with the HL, about 6x12 and 3000-3500 lb with hitch weight of 350-400 lb. Also until this summer I towed a KZ Spree Escape E14RB, about 2700 lb loaded, with several trips into the Rockies. Typical fuel economy towing is 11 to 12 mpg.
The HL is a good vehicle for towing, very stable and capable, except that on long grades at high altitude I would have to slow to around 40 mph in 3rd, sometimes 2nd gear. Also the transmission temp light started coming on during these tough climbs in 2013 (it hadn't done so before, and the dealership mechanics just shrugged). I elected to sell the KZ and buy a folding trailer, which lets me get 17-18 mpg and no strain at all on the HL. I'm still towing the cargo trailer for work though, and at low altitude around Tulsa it's absolutely fine.
I did use an Andersen No-Sway hitch for a year or so with the KZ, mainly to improve ride comfort (less jiggle over uneven pavement). Other than that I didn't feel a need for it as far as handling or safety. I had no problems at all with sway or anything like that.
I have not kept up with the changes they made to the HL in 2014, so YMMV.
Mike G.
Liberty is meaningless where the right to utter one's thoughts and opinions has ceased to exist. That, of all rights, is the dread of tyrants. --Frederick Douglass
photo: Yosemite Valley view from Taft Point