Separately, can torklift tiedowns be used on the used Eagle I'm about to buy? Anything special I should know? Or are torklifts overkill for the fwc's and the bed mount is better?
I think Torklifts are usable if the camper has jack plates.
Unpaved travel, in my opinion, requires more than the OEM eye bolts in the bed. However, just about anything works for pavement. Recently a member, Skeeter, safely traveled over 1,000 miles using ratchet straps.
Torklift, Happijac, and reinforced bolt through are all, in my opinion, acceptable. Bolt through is attractive both in looks -- no external tie downs -- and dollars.