The person asking the question, said that they had done some research and learned there were three methods. They wanted to understand the advantages of each and which they should use for their Class-A RV.
The mounted tire is placed on a balance and the heavy spot is counter balanced with weights. This is normally done with the mounted tire in the horizontal but I have also seen it with the tire on a special spindle as seen with this motorcycle tire as seen in this video.
The next best method would be with the mounted tire on a "spin balancer", This rotates the wheel and tire at speed and electronically calculates where to place the weights.
When you buy a new passenger or pick-up truck tire, this is the method they are normally talking about
But truck/bus size tires can also be balanced using a heavy duty version of this type of machine.
Spin balancers measures the up-down imbalance and the side to side balance and tells the operator how much weight to place on both the inside and the outside of the wheel to counteract forces in both directions.
Finally there would be "On-Vehicle" spin balance this would give the balance for the tire, wheel and the brake drum and hub of the vehicle so if the drum was slightly out of balance it would be included and weights would counter balance all the spinning components. If you get this type of balancing done it is important to mark the wheel position on the hub if you ever remove the wheel to check brakes and to re-mount the wheel in the exact same orientation. A downside to this method is that it can't be done to tires on drive axles.
but RV tires would be the same process but with HD bigger equipment.
I see little reason to balance the rear duals on a Class-A as you will not feel the balance problem unless something was very out of balance.
For Class-A I think you can just take the RV out for a quick test drive on a nice section of smooth Interstate. If you feel shaking either through the steering wheel or floorboards then you would go and have the front tires "on-vehicle spin balanced".
For Class-C and smaller vehicles using 16" diameter LT type tires I would spin balance all six assemblies.