I'm not able to advise really. Plenty of folk use 19s and 20s. Lots of info in forum.Hi
Have a van on order and looking to do something similar. They look great !
Could I get away with 19” or better with 18”
I went for 18s as I wanted cheaper tyres, softer ride and to have big profile tyres so don't have to worry about kerbing so much. I prefer the look of a big tyre on a van anyway.
It's all preference really.