I think the whole logic start in wrong point.
Unless you plan to tow ClassC, or Suburban, you can ignore GCWR.
That number usually come from hitch rating, what is easy to upgrade.
You critical numbers will be GVWR minus actual weight, what gives you cargo carrying capacity.
There is good reason why RV manufacturer hide those numbers from buyers.
Lot of RV have cargo capacity in hundreds of pounds >> not much for heavy family, full refrigerator, winter cloths and 60-100 gallons of fresh water.
Bottom line, when you shop for RV, step on the salesman to present those numbers, or drive with you to the scales.
Also might be good idea to check the tire ratings as lot of RV tires come overloaded from factory.