My experience is consistent with a lot of advice you're getting. I have backed up with the toad attached but only for VERY short distances (a foot).
When driving, I don't really know the toad is there - my mileage and performance are pretty much the same towing or not.
I am very picky about where I get gas. I need a large area not only for parking the motorhome + toad by the gas pumps, but also a good entrance and exit area. I usually aim for truck-stops on the major highways although a few Flying J's and Pilot's have been rather snug.
I have a "Protect-a-tow" that I very much like and I think it helps my gas mileage while towing. This is a very heavy mesh fabric that runs between the back bumper of the RV and the front bumper of the toad. In addition to keeping rock chips off of the toad, it also prevents air turbulence between the RV and toad. This contributes to better gas mileage.
I'd strongly advise developing a towing check-list. For me it is too easy to forget a step here or there...like "Turn off radio in car". I know if I follow the list, the towing will be uneventful. I have one list for the motorhome (setting up camp and tearing down camp) and another for the Toad (hookup and detatch). My helper just reads the steps to me. It goes fast!