It sounds like you have settled on a Sprinter. I think it’s a good choice, but I’m biased, having owned one for the past four years.
Where are you located? My advice for you is to reach out to owners in your area to look at several examples. I don’t have a hightop, but feel free to reach out to me if you are anywhere near the Bay Area.
Regarding running 35’s, Van Compass will be your only option.
Agile’s RIP kit only allows you to run 275’s.
“Flint” - 2016 SMB Sprinter 4x4 144" RB 150S w/ PH