I don't really know the specifics on the tank - a good friend has some and he'll lend me the tank. It holds like 20lbs, around 300+ balloons (evidently, how could I keep track really). No regulator, just crack the valve and fill your balloon. I like the punching bags =)
It is quite loud though, and there are silencer adapters, but my house it pretty sound proof it seems.
Theres automotive, food, and medical grade. Automotive grade has an additive to discourage use (tastes like shit and will kill your brain). Food grade is what your get in your little whippets or likely what you get at concerts. This is medical grade, it kind of turns you into a gas snob =)