Another poster, Live and Learn, also recently started a thread about RV'ing. She did not know what she wanted, whether a travel trailer or a motorhome, but she was talking about extended travel and not living in one full time. I think she had the same thing in mind as the OP of this thread, who already thought of a class B.
Now, the most important thing is to understand yourself and know your travel style. We have two stick-built homes that I like to come back to. Yet, I also like RV'ing. This means when I am on the road, I am traveling and not camping.
When going on a trip, I have a certain destination in mind, which is usually a few thousand miles away (nearer places have already been visited). I drive 300 to 400 miles a day until I get there. Once at the destination, I will linger at each spot for a couple of days or up to a week before moving on. I park the motorhome as a base, then use the towed car to go explore and do sightseeing. For example, when in Fairbanks, I used the car to explore the town and vicinity for a week before moving on. At Denali NP, I spent 4 nights, etc... You really do not want to drive a motorhome all over the place. And I tend to alternate towns and cities with national parks and boondocking spots for variety.
My current set up of a class C towing a car works out very well for my style of travel. Many RV'ers use a class A with a toad, but I would never want a class A. It won't go some places that I could with a C. Yet, I often found my C being too cumbersome.
Hence, I have been thinking about downsizing to a class B, which is small enough that I can use it for sightseeing and not have to tow a car. However, most Bs are so small that we may feel cramped on long trips. And a B large enough for more room would be too big. Perhaps a compromise would be a larger B such as the Winnebago ERA which is smaller than a C, yet powerful enough to tow a car if I want to.
I could use an SUV or truck pulling a smaller travel trailer, then park the trailer to use the car for sightseeing. I would never want a 5th wheel, the same way I never want an A. However, I prefer to have two motorized vehicles. If something happens to the motorhome, I can use the towed car to go get help. Yes, I am the belt-and-suspender kind of guy.
PS. In national parks, you see a lot of the Cruise America class Cs. People rent these to go see Yellowstone, Yosemite, Grand Canyon, etc... Driving a motorhome around the parks is no fun. My toad works out wonderfully for sightseeing, and also to go into the centers of cities like Anchorage, or Halifax. I also often leave the motorhome at a parking lot outside of town, then take the car to make a quick visit to the center of a state capital, or to scout for a place to stay a few days.