I may be wrong here but I believe that pressure is determined by tank size not a regulator. My 200,000 btu heater will not run on the small tanks because of insuffient pressure. I switched to the 100 gal tank and it works just fine.
Most 100 gallon tanks have a built in regulator when you get them. The smaller tanks do not as in the BBQ grill tanks. With those the pressure is regulated by the tank size like mtwaterguy stated. The 100 gallon is a higher pressured tank and will have a regulator on it to reduce and maintain the pressure. Then the larger tanks from 250 and up have an external regulator before it goes to the source.