looking to educate myself.
Since you asked, I will start with the fact that a fifth wheel has no steering wheel in the living area; that you need no toad; that the truck can be used for errands, sightseeing, and should the fifth be in the shop the truck is still useful or if the truck is in the shop the coach is still fully liveable. As far as some of your questions go the quality is like any other RV, some are very high quality and some less so. A Ford diesel 250's fuel mileage will depend on lots of variables not the least how you drive and how much weight the fifth weighs. As far as tipping over, that is likely not a serious issue depending on how you drive safely. A couple downsides to a fifth is that you cannot get up and make a sandwich, use the bathroom, etc, while somebody else driving.