I was a spontaneous young traveler, and very much a planner now. Part of this derives, I think, from the fact that the stakes are different when it’s an entire family rather than a young and mostly broke student. I also like good value and a little advance planning often gets you a better quality of lodging, easier itineraries, or lower prices. So the transportation and lodging gets done way in advance. The day to day activities are relatively freeform.
At some point in the future, I’d love to do a completely unstructured solo trip.