Pyrate, as a semi-retired consulting geologist I’m pretty much doing what you plan to do, using my 33’ Class A Holiday Rambler as a base camp and a Dodge Caravan and 250cc dirt bike for exploration. If I had to do it all over again I’d probably get a shorter RV, possibly a Class C, no longer than 30’ with lots of ground clearance. Early on I had such a problem with tail-dragging over any kind of a dip I finally installed rear suspension air-bags in my RV to raise it higher, that’s the main reason I’m suggesting nothing over 30’, that long rear-end overhang can be a royal PITA for boondocking!
My RV before I installed the rear air bags. Just look at how long that rear end extends past the rear wheels!
My intrepid 27mpg Dodge Caravan exploration vehicle on a 2 month 12,000 mile Western Canada/Alaska road trip. Using my Caravan for this trip, rather than my RV, saved me about $3,000 in fuel costs!
Early on in my adventures I visited Yosemite. No way could I get a campground in the park. However, I found a beautiful and half-full National Forest CG to stay in for about $5/night just outside the park. When I visited the Grand Canyon North Rim recently I just pulled into the nearby National Forest and camped for free. It was nice looking out my window in the morning at a small flock of turkeys just outside!
Steve
PS what size RV to get is very subjective and depends largely on how much space you feel you need and what and where you plan to go with your RV. If you're going to do a lot of one lane gravel roads, then a small 4WD RV with lots of ground clearance. Since I just use my RV (home-on-wheels) as a base camp I can get away with having a huge ponderous interstate cruiser RV to travel from one area to another, knowing that I can explore all over in my Caravan or dirt bike once I land.