Hi; Looks like your well on the way to understanding and making a decision that meets your needs and desires. I drive a 2016 F350 Lariate 4x4 SRW and it has handled my 3660RL Monty just fine. I am right at the limit and have to be extremely careful of my onboard cargo and weight distribution. Anyway, I just wanted to point out that the 2020 F350 Towing guide (page 25 note 4) limits the 5th wheel max weight to 18000lb due to its factory installed 5th wheel hitch limitations. Not sure of similar limitations with the other vehicles. (
https://www.fleet.ford.com/resources...uide_Sep26.pdf) Lastly, the only true way to calculate any of the important specs is to weigh your trucks front axle and rear axles weight without the trailer but with normal load of passengers, tools, or whatever you normally carry in the truck. Then do it again with the trailer noting your rear axle weight again. With those figures you can make all the calculations you need to see if you are within your comfort range. For example my truck weighs 8593lbs with me, my wife, some tools, 5th wheel Hitch, folding tonneau cover, etc . So my GVWR 11500lbs - 8593lbs = 2907 lbs left for other cargo or PIN Weight. The newer trucks weigh less so that's why their available cargo / payload numbers have gone up as well. Anyway, good luck with your research.