My experience is when my jeep was, "new to me," flat towing was all I had available (late '70's). I'd break down and then need a tow home or a repair was needed that I didn't understand/ couldn't perform so a flat tow to the garage was needed. We didn't use a safety chain so I stayed in the jeep during flat tow - in case the hitch popped off (plus the steering didn't track too well on sharp turns). I've learned since then. Regardless of what you tow or how you tow it, make sure you have a chain! There are horror stories where things come off and become an uncontrollable projectile on its own path! Think about that when your closure rate with on-coming traffic is near 100mph.
IF you only go 55 mph, I suspect flat towing will be fine. It is within the speed limits of the jeep (that posted 60mph limit is with gears and engine engaged). The problem is, I've noticed when towing a trailer on the highway, I look down at the speedometer and I'm up to 75 mph. While it's been done, I don't think that would be wise while flat towing. The bearings could handle it. The differential gears could handle it (assuming of course that maintenance is up to speed and parts are within specs, i.e. not dry, loose, etc). I'm not sure about the transmission/transfer case gears spinning that fast though. The output shaft "should be" the only thing turning. From my limited experience, I can't imagine the transfer case dropping into gear on its own but I suppose it's possible.
A dolly is okay (I've used one) but now prefer a dual axle trailer. I think I'd load any vehicle forwards on a dolly unless there was a mechanical reason not to do it that way.. I would probably also tow with the w/s down regardless of direction.