The board shall: prepare and recommend a compensation plan, a classification plan, and comprehensive regulations governing operation of the merit system; and submit its recommendations to the Commission for adoption. The Commission may adopt, disapprove, or modify a recommendation of the board. If the Commission does not act on a recommendation of the board within 90 days after the date of filing of the recommendation with the Commission, the recommendation is deemed approved. A recommendation by the board for an amendment to an adopted compensation plan, classification plan, or regulation is subject to subsection (b) of this section.