I used a truck with slide-in camper for the same purpose you're looking at, just exploring state and national parks and camping in the electric only sites. The truck had 4x4 but honestly, I never used it on any state or national park roads that I used to get to the lakes of hiking trails. The only time I used 4x4 was to get out of swampy ground when I tried to park it too far into a ditch. My biggest problem was having to completely put everything away in the truck and have to exit the back of the truck camper multiple times a day to get into the cab of the pickup truck and vise-versa.
I sold the that camper set up and bought a 1993 Airstream B190 van for 10k with 80k miles. It's only two wheel drive, but I drove it through Uwharrie National Forest roads in North Carolina, and around the Outer Banks. Of course you have to know what you're driving on with 2wd, but if you add a locker to the rear you would be golden for any regularly used park roads. The best part with the B190 (or any small class b type RV camper van) is that you have all the creature comforts of home. I full shower, toilet, oven, stove, couch, microwave, tv, queen size bed separate from the couch (over the cab) and BEST OF ALL, a passthrough between the living area and the cab of the vehicle. When weather is horrible, I can clean up everything in the camper while I'm still in my pajamas, then sit down in the driver chair and start driving to the next destination.
Also, the Ford E-series vans are easy to convert to 4x4 on your own or there are plenty of conversion companies out there. But I'd recommend leaving it 2wd, adding a small lift, and locking the rear.
Just food for thought.