I need some guidance deciding what size tire to buy. I'd like to go as big as possible with minimal (or no) rubbing, and without a lift.
Referring to the linked chart: I found one ST tire (GY Endurance) listed among them. Should not be used on a truck, or van, because of the sidewall stiffness. A LT tire is the way to go; not quite as stiff a sidewall, but better performance all-around (perhaps not, on heavy tandem trailers).You might need to get on a forum for your van to find out exactly how big you can go, but here are the options in ~33" tire: https://tiresize.com/tiresizes/33-inch-tires/
If you are off road a lot, you might go with an MTR, but if you are 90% road and 10% light trail, go with an All Terrain (AT) tire.
It's all about a little give-and-take. It's not really an either-or situation.
Could go a bit bigger but would hate to have to mount the spare on the exterior of the camper.