Yes, Pick up trucks with slide in campers can purchase a car/tent spot.
They have additional charges for deviations from the typical car tent camping. RV spots are certainly purchased separate. Look at the FAQs on their website. They were just changed for 2019.
Yes. As long as the camper is on the truck and fits into a Car Camping spot, you should be just fine. However there is no power or water hookup without purchasing an RV reservation.
Should be able to. All spots I've camped in have room for the vehicle and then a couple tents. Assuming that you're not towing the camper then a standard car site should be fine. If you're towing, then you might need a larger camp site.
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