The difference between a DRW and SRW is the Cargo Carrying or payload capacity of the trucks. There is more to towing than GCWR. A typical 5er will have a loaded pin weight of 20 to 22% of the trailers GVWR (ignore the brochure pin weight).
Look at the yellow sticker on the truck for that particulars trucks payload capacity.
Take the trailer estimated pin weight + the 5er hitch +any cargo in the bed + passengers. This total should be less than the trucks payload capacity.
The DRW will ALWAYS have a higher payload capacity and rear axle GAW than a SRW.
A long bed with a longer wheel base will ride better loaded or unloaded than a shorter wheelbase truck.
I would NEVER a 5er with a short bed truck. I see too many short bed trucks with busted rear windows or dented cab. Towing RVs since 1984 and 5ers since 1999.
So the net results is to estimate the real pin weight and see if it is enough truck to haul the trailer, not just tow it.
Ken