I've done it lots of ways, solo, with DH and on a big organized ride (RAGBRAI). Solo is fun because you don't have to please anyone but yourself. With someone is fun because you have someone to bounce ideas off of. It is also a friendly way to go. Organized rides are neat because the route is already planned and all you carry on your bike is your normal daily stuff.

Having DH along also means someone else gets to share the weight of the tent & cooking gear - unless this trip is a credit card trip, where they are not needed.

All approaches are valid and fun. You don't need to go on supported tours before a solo tour unless you want to. In my experience, a supported tour is more about Bicycle Culture, whereas going solo or with a trusted friend will give a better sense of place and people that you encounter. Both are valid - but different.