I always knew I wanted to travel, so when I went full-time with a new Class C motorhome in 2012, I had no problem "adjusting" to a smaller space at all. However, my C is 32' long with two slides, but I have been perfectly comfortable living alone in this small space for the past 9 years! And I hope to do so for another few years, at least. I have never towed a vehicle, so I take my motorhome with me when I want to sightsee or shop. I have driven 157,000 miles in 9 years, so I keep moving and stay almost entirely in state, national, and county campgrounds. I like the space and privacy in such places, as well as being able to be out in nature, NOT close to towns.
Now, I admit, if I were two people, I would probably be more comfortable in a smaller A because of the cargo carrying capacity and just a bit more space.
The big question on the type of unit to buy is how you plan to full-time.
- If you plan to keep on the move, staying a week or two in various national and state parks, as I do, a motorhome is a very good choice for several reasons. It is easier to hook up and unhook, assuming you do not need a towed vehicle. So, within 4 minutes, I can put in my slides, unplug electric, and leave my chairs, etc. outside to make a quick stop at the dump station, then return to my site. Since I have no towed vehicle, backing in is quick and easy. It is also a luxury to pull over at a rest area and fix a sandwich and use the bathroom without going outside. You can also flip on your AC using your built-in generator so can be comfortable. I stop for groceries and such as I travel between campgrounds.
- However, you mentioned "settling" in Florida for the winter and also in the north for summer. That means you prefer commercial campgrounds for months at a time. If that is true, you might want to consider pulling a 5th wheel with a pickup truck. (5th wheels have much more storage than trailers, by the way.) Commercial campgrounds, especially in places like Florida, offer pools, hot tubs, and activities, but you are almost always parked within a very few feet of your neighbors, to the point where you can hear conversations and listen to their TVs. (I had to spend 4 months in such a place a couple of years ago to get medical treatment, and I could hear the dogs next door racing back and forth in his trailer! It is easier to make friends that way, if that is what you want to do. You can leave your trailer or 5th wheel sitting in the same spot with full hookups and drive your pickup truck around. But you can still do some traveling if you want to do that as well, but your total rig will be longer when you travel, and it will be a little harder to get into and out of gas stations and campgrounds.
I hope this helps. Some people say they started out in travel mode and then settled into a semi-permanent lifestyle, but maybe you will be like me and prefer to keep on the move. So think seriously about how you want to live "full-time."