Couple things...toy haulers are built to carry the weight of toys behind the axle and still have adequate pin/tongue weight. When there are no toys in the garage, and no offsetting weight behind the axles, they are impossibly heavy on the pin/tongue. Planning to use a toy hauler with no toys is not a good idea.
How are the thinking of living in the RV? If they have a place to park it, a 5er is probably the best choice. If they have to stay mobile, then a MH is probably better.
FWIW, I have about 4" more headroom in my Lance TC than I did on my 34' Terry TT. Ceiling height is more function of RV type and manufacturer than whether Class A, B, C etc.