Most Low Pressure Markers have a vertical reg(foregrip), So with the tank reg, then the vertical reg, you will have a two stage air set up. In this case you can use either HP/ and some LP Tanks. With HP tanks you will have fewer problems with the recharge rate of the vertical reg, which leads to drop off at high rates of fire.
A single stage set up are when you have the reg on the Tank only, leading to a gas thru vertical grip and on into the gun. This is when the LP tank comes into its own.
LP Crossfire tanks do have good recharge rates, as stated above.
so, with two stage regs = HP/LP Tanks
Single stage reg = LP Tank