The calculations I did on my F150
Payload: 1,813lbs
Tow Rating: 11,700lbs
Payload 1813 - occupants (5 people) 550lbs - WD hitch 100lbs - 120lbs of kids bikes = 1,043lbs of payload left for tongue weight.
Ideal travel trailer tongue weight is 10-15%. Lets say 13% for math.
Travel trailer max weight if I wanted 13% tongue weight: 1,043/0.13 = 8,023lbs.
My trailer is 6700lbs as per the yellow sticker on the door.
Wet and loaded for the road, my tongue weight is 950lbs per my Sherline tongue weight scale.
I would do a similar calculation for towing a 5th wheel if it were up to me, which would put me in an F350 for sufficient payload (ie. 3500lbs)