I do not know that you can predict sway. I towed a 25 ft. TT with an underpowered 2002 Ford F-150 2x4. Very poor performance but no sway.
I now tow a 25 ft. Dutchman with an E-Boost F150 4x4 and no sway issues. I have the Blue OX WD hitch the dealer installed when I bought the trailer. I do not have any anti-sway apparatus except for what is supposed to be part of the hitch design. I also tow at 60 mph.
Still there are many who go to great lengths to reduce TT sway. I think it is a function of TT design and/or the TT and TV compatibility.