new wheels & tires

Hi guys, I'm new here and just bought a 2003 Astro. I'm looking at tires and wheels for it. The van will have Journeys 3-5 kit on it.
I'm wondering what offset and backspace I need, and should I stay with 16" or go larger? Wanting to put as Tall of a tire as I can and not rub off-road.The van will mostly be on pavement, but when it is off-road it will be on gnarly Hawaiian back roads.
For 30+ years I have always used BFG A/Ts on my trucks, but got a bad set on the last round so I sent them back and got Nitto Ridge grapplers.
I can worry about tires after I figure what size wheels to go with.
Any suggestions?

Thanks