Insurance and Rv value

You can ask your insurance agent if they will write your policy as "agreed value coverage" which will give you a fixed amount IF the vehicle is deemed a total loss. If they will, they may require an inspection and if they agree, then you can use NADA values, or any other book that they allow. They will not allow you to pick a $100,000 value for an RV that is only worth $50,000 per the book, BUT, if you have some very special modifications, most companies that write agreed value coverage will allow you to add some of their value.
Do not expect this type of coverage to be the least expensive.
Actual cash value is usually determined by an average of various value books that are out there. Any improvements and maintenance items are usually not considered in the final value.

It will be a negotiation between you and your insure company. ACV should be what it actually costs you to replace your unit with a comparable unit including taxes. If NADA says $100k, but your insurance company finds other similar units for sale for $75k then $75k is going to be the price. If NADA says $75k but you can't find anything similar for under $100k then $100k should be the price. It will all be a negotiation.