For just taking the family and travelling a Class C based on the Ford or Chevy 450/4500 Chassis is plenty with the gas engines be they a 6.8 liter V-10 or the 6.0 V-8. Both will pull a 5000 lb or so Toad for side trips and do so with relative ease.
As was mentioned before Super C can by some manufacturers be nothing more than a standard C type motorhome but usually in a 32+' length box.
Others will call something "Super" for going to a heavier chassis, suspension, and a diesel engine to gain additional towing capacity. ie; someone that wants a 30+' box for the house that the rig will also be pulling a 25-30' trailer with a few toys like SxS or maybe a pair of Harleys along with dirt bikes.