I'm guessing the OP already made a decision on type of van to purchase, but wanted to add my experience for any future thread readers.
Like the OP, my hubby and I are campers and do not plan living in van full time. We intentionally purchased a passenger/conversion van in 2017 to save us the time from building it out from scratch. In just a few days, with our old camping gear and some unused items from the house, we were able to go camping in it. We loved it instantly on the first trip.
Since that first trip in 2017 we have camped all over the east coast, trips usually 2-4 weeks long, culminating with our 9.75 month 16,000+mi excursion throughout the western US this past year.
Addressing some concerns raised in this thread:
1) extra seats
we kept the back seats in our attic for a few years in case we wanted to sell van in future. After deciding to keep van to its grave, they got sold in a matter of hours on craigslist.
2) insulation
We have added no additional insulations to walls of our van and have experienced temps anywhere from 110°F (during heatwave in Seattle area last yr) to 18°F (March in Bryce). We found that we can comfortably survive in van without needing any additional heating/cooling appliances when > 40° and <90° in dry areas, and >45° and <80° in very humid areas with our handmade reflectix/felt window coverings, that we flip depending on cold or hot.
Outside those temps , we have been perfectly comfortable with electric heaters or fans. The only time we can't stand being in van at all when temps are very hot or very warm *and* very humid.
Also, not living in it full time allows you to pick the seasons to travel so insulating from extreme cold and heat is not as much a concern.
3) windows
Being able to open many windows has saved us from having to cut a hole in roof for a fan. There is ample ventilation.
One of our favorite moments is laying in bed in the evenings or getting up in the morning, looking out of the windows to nature makes camping even more magical. We could go outside during those times, but our bed is more comfortable.
As mentioned above, the reflectix/felt window coverings provide ample draft/heat projection.
4) carpeting
We never had moisture problems with the carpet and we live less than 10 miles from the Atlantic Ocean. A vinyl floor sheet was laid on top of it a couple years ago bc we hate carpeting but didn't want to go thru time/effort to rip it out... plus we thought it would help with insulation and sound reduction.
Neither of us has regretted the decision even for a moment to buy the passenger van over a cargo.