what gas engine? 2020 F350: 6.2 Gas or 7.3 L Gas?

That’s exactly my thoughts, I’d be hesitant to be one if the “guinea pigs” of an all-new design, and I’m more than 100% sure the 6.2 has plenty of power because for decades I carried a lot more with less. It’s stronger than my diesel was when it was stock.
Payload won’t be an issue for you, an F350 isn’t and hasn’t been built that won’t easily carry that camper regardless of what the so-called “rating” is.