I tow a moderate sized trailer for work via bumper pull, and it's about 6,000lbs empty and can be 10,000+ lbs loaded. I never use tow-haul mode for the trailer empty and usually only use it when I have the trailer pretty well loaded up roughly 9k+. I don't like how it shifts with light loads at all and non-towhaul works just fine. I love how it adjusts to heavier loads though and it's excellent for the increased weight.
When towing our 11,000lb fifth wheel via gooseneck conversion, always tow-haul mode and it pulls like a dream.