I agree that temperature is by far the most important.

In my case, I lucked into buying a house with a walk-in fridge (the
previous owner was a hunter who owned a refrigeration company - how
lucky for me!). I ran into problems with humidity and vibration, as
the cooling unit hangs inside the fridge and the fans run constantly.
The walls vibrate when the unit ran, and since I was only running the
cooler down to 55-60F, the unit didn't get enough condensation to drain
out the humidity, leading to an unexpected mold outbreak on the outside
of my corks. I found racks that I could free-stand to avoid the
vibrations. But for humidity control, I now use a container of
"Damp-Rid", which condenses humidity and catches it in a little cup.
I'm not measuring humidity, but I can tell you that the whole mold
problem is gone. Found it at a big box home-interiors store.

Rob