We have done 4 adults, 1 dog in a roof tent + awning room combo out of a jeep JK. We were over payload, by a good margin, but in terms of space for sleeping, there was plenty. I'm bringing this up as it can represent another option besides the slide-in camper, and that would be to take a more modular approach to your truck. You can easily get a bed rack or a decent cap and outfit your truck with a tent and awning with room, which would be both lighter and way cheaper than going for a camper. You will get a cream-of-the-crop tent, cap, and awning with a room for well under $10k. A bed rack and more middle-of-the-road products could be done for about $6k, maybe less, and I'd wager that this mode would only weigh about 300 lbs (That's an estimate based on dead reckoning).
In our case, two adults and the dog were up in the roof tent, which was a 3-person model (Tepui Kukenam). 2 adults were down in an ARB 2000 awning and room, with a floor, and they were spoiled for space (could fit at least one more adult in there). We're currently in a king-sized Roof tent, which has room for three humans (granted one is tiny), two dogs, and a cat but with this grouping we actually don't need to use the awning; we would run out of seats in the truck before we run out of places for people to sleep. And, there are even bigger roof tents that offer internal dividers so your roof tent functionally has two "rooms".
Between the tent and the awning, you can then build out the back of your truck however you want. For us to mount the tent and awning takes about 40 minutes - less time than going to a storage unit and back - and it's far easier to store than a full camper. Plus, there's no harm in leaving it mounted the entire time.