If you are not sure the best option for your needs, the best answer is to rent.
First choose a model that you think fits your requirements. Use the vehicle for a couple of weeks or even more. Drive it, camp in different kinds of parks, with different kinds of hookups. Live in it. If you are thinking you are on the short list of "full timers" this is one way to find out if the freedom of the road is as free as you want it or if the walls begin to close in on you.
If you have rented an RV, you will not have the initial investment to worry about. Just return to the rental agency and try another style or size.