I think this is a case of a physical test is needed. I'd expect not needing a WDH at all with the Expedition. With the Explorer, without a WDH, it's doable but likely an uncomfortable tow.
Your posted weight specs are confusing.
I had a 1998 Expedition with tow package, 5.4L and routinely towed a 10x6x6 cargo trailer loaded with about 3-3.5K# of band gear (with more in the TV). Hardly knew it was there going forward, stopping without trailer brakes was another story ;(
Bought current TT with a 2008 Explorer with tow package V6. GTWR 3877#. Was going to try w/o WDH going home, dealer talked me into a good priced used WDH that they set up perfectly. Glad I did, towed great but just moving the TT around the yard on a basic ball mount dropped the Explorer rear significantly.
Towing that same TT with 2019 F150 tow package V8, still using that WDH. But I screwed up and lost a WDH spring bar on a 60-70 mile tow so I towed it home with a basic ball mount. Only difference was a little TV rear drop and I felt the Lake Erie winds more so I drove home trying to keep at 60-62mph vice my usual 65mph & faster downhill.