The car or truck manufacturers are covering their a***es thoroughly with their rated tow capacity. My 5,000 rated SUV does fine. It has a "sport" driving mode that might as well be called towing mode. It locks out top gear. It will tow the boat at 60 mph up any superhighway grade I have encountered at part throttle.
As far as braking, you do need to make sure your trailer brakes are properly maintained and functional. If so, the trailer will not contribute significantly to the vehicle brake demand.
As far as loss of control, I have had a tire blowout on my single axle trailer at 55 mph. loud bang, lots of rumbling, but absolutely no impact on directional control or stability.
I don't know what else to say. It works. You do have to drive intelligently and defensively, but that's true of any trailer towing undertaking.
Larry