The large majority of "towing threads" that I've read here mostly talk about size of the towing vehicle, frame, suspension, tires, brakes, and especially the transmission. Actual "power" of the engine usually comes last. I've towed using little 4 cylinders to big honking V-8 gas and diesel engines, I just adjust how I tow depending on what I'm driving.
Size and power of the engine certainly gets talked about with the "towing mileage" threads. Big engines, depending on the rig, can get better fuel economy on the highway without having to rev very high.
In general, for me, it is "no fun while towing" if you are running over 3,000rpm for hundreds of miles. An engine just quietly loafing along while towing is a nicer experience.
Now that I've solved all those problems, off to solve boondocking issues... lol!