In my opinion, The Franklin is most likely post-Enterprise NX-01. (Say Say they were using a warp scale of warp^2 on "Enterprise" (and that the display on "First Flight" showing warp^3 was wishful thinking on the engineers' part). So, "old warp" 8 = 64 x light speed = "new warp" 4. As far as the transporters only being rated for cargo; maybe the Enterprise was just using it for humans/lifeforms the same way Scotty was - by the seat of his britches.
It just doesn't make sense that they would go to NX-326, then to NX-01 (unless they were trying to confuse the Romulans!).