Beer cellar, aging, and corked beers

I am about to convert an interior closet into a beer cellar. I am curious what people think about aging corked beers regarding humidity levels. I have read it does not matter as long as it's not bone dry in the closet. I have also read that you need to keep it at around 60% humidity. I don't have a ton of corked beers aging, but I have about a dozen. All of the others are capped and humidity does not matter.

I plan on insulating the walls and door. I also plan on installing a portable AC unit that will vent up into the attic.

Any thoughts?