Some questions on National Park sites

My DW and I would like to start full-timing in the future. We expect to do lots of hiking during the day and some work during the evening/night. We MUCH prefer to camp in less open spaces that feature its own picnic tables and fire pits.

Fulltiming is not the same as recreational camping. You will have all your life with you, no home to go back to, need to work perhaps, and will want to stay longer in places than the typical recreational RVer. That said if your priority is to be able to put the RV in the most maneuverable places, tightest spaces, etc. then get the one ton and get a cabover camper or a B van. You will be giving up interior space for maneuverability. If, however, you want to have space inside then the trade-off is size and resulting manueverability. Most national parks in the US have limits on stay. Most RV parks have monthly rates that are very favorable compared to national park daily rates. Most full timers like the amenities of being able to hook up the sewer, water and electricity. Most national parks might have a shared water spigot and none of the other items. In a national park you will be camping next to recreational campers and in some ways it is a release for them from their daily city lives. That means some crowding, noise, lots of activity, pets, etc. Most RV parks that cater to full timers are typically less busy. Some folks absolutley have to camp inside the park or they are missing out on the park's ambiance. Many national parks still require a drive or bus trip to see all the features. So, camping outside a park in a less busy and possibly larger campground that requires driving to the park a few miles away is not all that different than staying inside if 'inside' is not the absolute requirement for camping for you. You still can do all the hiking and biking you want or could do inside the park, just doing it from a different base camp. If your part time work requires internet, that might be an issue in some national parks as well.