We have 2017 4Runner TRD Pro pulling a
Lil Snoozy, unweighed but estimated at 3000 pounds. Tongue
weight measured at 320 pounds. This model is part time 4WD (not all wheel drive) so towing is almost always in two wheel drive. There is barely any rear suspension sag.
So far after about 12,000 miles of east coast, Appalachians, Midwest, Great Plains, and Rockies there have been no problems at all. Gas mileage towing at about 62-63 mph is about 15.5 mpg. There have been no sway problems at all and I prefer the body-on-frame construction for towing.
We have towed in both overdrive and in 4th but almost always in 4th now. Highest transmission fluid temperature out (before cooler) is about 230 F.
Towing up hills in the east on almost any Interstate highway is easy at 65 mph. Steepest hills are easy going 60 mph at 3500 rpm. In the Rockies at high elevations, e.g. 9000 - 11,000 feet you have to slow down and downshift. If you don't like that, go to a Denver dealer and get the supercharger installed for $7500. I don't think it is necessary but might change my mind if I lived at altitude.
I think the 4Runner is a great tow vehicle for this size trailer and have no regrets.