So much info online...

Depends on your needs, who, what you want to bring and your amenity requirements.

Bigger vehicle is better, but also means higher cost (gas) and less opportunities to go stealth (parking lot).
Vehicle choice may also depend on climate.

I see a lot of MB Sprinter conversions.
They seem to work well, as you have plenty of options for the body style.
Would be too big and unwieldy for off-road and city driving + you'll stick out like a sore thumb if you try to stay ON in a mall parking lot.

Most of the smaller camper vans offered in the States (VW California, MB) are outrageous expensive and not worth the money, IMO.

I always went stealth.
Wanted to be able to park and sleep wherever I wanted without drawing attention to local authorities (even had commercial decoy decals made).
I have used::
Station wagon < Minivan < Small Delivery van

Traveling alone, I found the Minivan to be a good compromise regarding stealth and comfort for Tri.
It can be pimped with a second battery for some amenity mods such as fan/heater, mini-fridge, and with AWD still be suitable for camp-ground with a tailgate tent.
But MV mods also require quite a bit of DYI.

Again, too much info online.....If you don;t care about stealth and AWD, Chevi Astrovans may be a cheap ticket, if you can live with their burden of age.