At the direction of the appropriate district council, the Commission shall initiate and adopt: a general plan for the development of that portion of the regional district located in each county; and amendments to the general plan. Notwithstanding the provisions of subsection (a) of this section, the Commission shall review, 2 years after each decennial census of the United States, the general plan for the development of that portion of the regional district located in Prince George’s County. In accordance with Subtitle 2 of this title, the Commission may initiate and adopt any amendment to the general plan. The appropriate district council may designate a functional master plan, an area master plan, or an amendment to either plan, as an amendment to the general plan.