HP and tank size has nothing to do with instantaneous pressure available at the end of the hose. If your tank is @ 200psig and no air is flowing, the pressure at the end of the hose will be 200psig. If you open a tool and flow goes to 10cfm, the pressure will drop relative to the friction loss in your hose, regardless of the HP or tank size. Fora hypothetical example with a 50', 3/8" hose, pressure will be 150psig @ the end regardless of the size of the compressor or tank. The tank size has an affect on how often the compressor cycles on and off, assuming the compressor has an output larger than the use. If the compressor is smaller than the use, then it will come on and stay on , regardless of the tank size and pressure will slowly drop in both the tank and more at the end of the hose until pressure drop is large enough to balance the compressor output. Tool power will be significantly less than optimal after you blow down the tank for an undersized compressor. 3/8" hose is plenty for the majority of air tools, as long as hose length is 25' or less.
I can say categorically, a 2hp (~3-4cfm) compressor is undersized for all power tools, especially air hogs like paint guns and DA sanders. Units that small are intended for nail guns, air brushes and the like. 5HP (~10cfm) is a minimum for the basic tools of interest to auto hobbyists.