I think the manufacturers are getting just a bit crazy with: "I mean for 2021, the 3.5L makes 400 hp & 500 lbs-ft of torque w/ tow rating of up to 14,000 lbs! In comparison..."
An F150 or a 1500 really has no business pulling that kind of weight, especially if it is a 5ver or a TT with the front sail wind loading. (A flatbed or boat trailer is different). While I'm still good with people towing a 7 or 8K trailer with their properly set up and spec'd 1500 at times, this unceasing climb of gcvwr is getting out of hand. When the trailer is longer and weighs more than the tow vehicle you start to have some real issues with emergency maneuvers and braking.
This from:
Are You Hauling a Safe Weight? Simple Checks to Know if Your Truck Can Haul Your Trailer Safely
(Begin copied portion of article)
Don’t Make This Common Mistake When Looking at Towing Ratings
"It’s simple - don’t assume you are hauling a safe load until you have considered all of the factors in your towing set up. If you know that your vehicle has a Gross Vehicle Weight Rating (GVWR) of 9,000 lbs and your new trailer model weighs only 6,000 lbs, don’t assume you are ‘good to go.’ This is the most common mistake made by consumers and can lead to some dangerous situations.
"What happens is that vehicle manufacturers tend to brag about how much their trucks can pull or tow, but they generally fall really short when it comes to the capacity of the hitch and the tongue weight the hitch is capable of carrying,” Brad explained. (Emphasis mine)
This is like having a large suitcase made of the strongest material in the world. It is capable of holding an enormous amount of weight, but when you try to pick it up, the handle breaks immediately.
“Remember that the load is only as safe as the weakest link. If you have a vehicle that can haul 12,000 lbs but the hitch is only rated to carry 500 lbs, you better not have any more than 500 lbs on the tongue weight or you are running the risk of getting into a serious accident!”
...he is looking at a new total weight of 6,800 lbs. His Ford F-150 has a towing capacity of 9,000 lbs. Brad chuckled, “So you would think we’re in great shape, right?”
In reality, this is a poorly matched truck and trailer. The hitch on Michael’s truck has a max gross weight of only 5,000 lbs and a max tongue weight of only 500 lbs. “Why in the world a manufacturer like Ford would create a truck that can haul 9,000 lbs, and then put a hitch on the back that can only handle 5,000 lbs and a tongue weight of 500 lbs is beyond me,” Brad exclaimed.
Even a weight distribution system on the hitch would not be enough to pull the trailer safely. The capacity with a weight distribution hitch increases to 10,500 lbs max towing weight, but the maximum tongue weight is still only 1,050 lbs. A weight distribution system on a hitch helps a vehicle handle a larger hauling load by taking some of the weight off of the tongue and distributing it onto the other axles."
(End copied portion of article)
The other issue is the limitation in your owners manual on the trailer's frontal sail area, often 60sf. Frontal area limitations are primarily tied to GCWR. The stated GCWR for your tow vehicle assumes the frontal area of your rig is less than the frontal area limit stated in the owners manual. The more frontal area, the more aerodynamic drag your rig has, requiring more power and torque to drag that big wind sail through the air.