Imho 18” wheels are the best for comfort and tyre price. 20” easily kerbed, 19” tyres expensive!
IMHO 17" wheels with BGF KO2's are the best for tyre price as they seem to last forever. They offer the best protection against kerbing, prevent getting stuck in a field, good in snow and look rad!
However, they are noisey, use a bit of extra fuel and are not as grippy on tarmac. I therefore now run summer 19" wheels. (Sure the tyres are quite expensive, but heck, we are wasting money on modding vans here which as my better half points out is very wasteful. "In for a penny" and all that!)
My wife likes black wheels and I like shadow chrome wheels for my van and run these all year round because I don't ever leave tarmac other that an occasional gravel track.
My T32 van is a Sunday best work van and I run KW1 coilovers and am delighted with them.
My wife's T30 camper runs STX coilovers (which are pretty much exactly the same set up as the KW1 on my van), but we now regret not having a different suspension set up which provides out and out comfort. In hindsight it was a mistake going with coilovers on the camper and we are fine living with it, but would do differently in the future. This is a case of horses for courses and all that........ Why have a coilover setup on a vehicle which is a mobile bedroom/kitchen! It's a bit daft in hindsight!
I say all of this because........ there is no right when it comes to taste, but lots of "wrongs" when it comes to functionality.
What are you planning on using your van for? Is it your daily drive? Do you need to park in multi storeys? Will it ever be used on pitches in the winter? Are you a closet hooligan that likes chucking a commercial vehicle around tight bends like it's a Lotus Esprit? Do you prefer to just arrive in comfort and be less concerned over performance?
All of the above dictate that there isn't a quick answer to the original post.