There was a discussion not to long ago about the size of frig to use plus one that had brown discs to show different model refrigerators could handle.
Many would hold two to four 5 gallon corny's then only a couple 3 gallon on the hump of the compressor or less with a small Co2 bottle inside. From what i've read is that the 5 to 6 plus cu/ft chest was the way to go allowing for many corny's,. I would think about your expanding your system in the future finding out the chest will not handle your needs. Like a gun safe always buy larger than you'll need as you'll expand and fill it in a short time anyhow. JMO's, did it twice on the gun safes.
My welding and local HBS were both against having the bottle and regulators inside the chests or refrigerators due to the moisture enviroment on the regulators and gauges. A little hard to hide a 150 cu/ft Nitrogen mix for the stouts unless a long remote line is used, my only choice.