Car Insurance Costs
With the majority of companies, a prior insurance discount for auto coverage is based on being previously insured under an auto policy. Unfortunately most companies won't consider an existing motorcycle policy to be sufficient to qualify for a continuous insurance discount.
Your RV and your vehicle are considered two different types of risk. Automobiles are covered under a personal auto policy and recreational vehicles are covered under a "special lines" policy.
While it is correct that your home will need a separate policy for flood coverage, you do not need it for your auto insurance as long as you have comprehensive coverage. Comprehensive covers things like fire, theft, vandalism, and flooding.
A golf cart is covered on a Special Lines insurance policy since it is a different type of risk from a traditional automobile. Unfortunately that means you won't be able to add it with your vehicle, but most insurance companies offer discounted rates for "bundling" your two policies.