A class C is built on a cutaway chassis. Length, height, no. of beds and where they are make no difference.
A class B is built on what is or was a van chassis. Examples are the 2 vans at the header of these pages. A couple models of Roadtrek and Pleasureway were built off of vans and the upfitters cut the original body out behind the front doors. Examples are the Roadtrek 200 and 210 Chevys and the Pleasureway Excel Fords. They look like small class Cs, but they are Bs.
The B+ term that LTV and a couple of other makers use is a marketing term they created, not a true definition of an RV type. Hope this helps....
Again, the Wonder RTB is a REALLY nice RV. Really nice....
Bob & Sharon
2019 Winnebago Travato K (2018 Chassis)
Past RV's: 2013 WGO ERA 70A, Chevy PW Lexor
Itasca Navion, 29' Jayco 5th Wheel