(a) Except as provided by Subsection (c), participating governmental units may by joint agreement determine the number and qualifications of members of the governing body of a commission.
(b) At least two-thirds of the members of a governing body of a commission must be elected officials of participating counties or municipalities.

(c) The governing body of a commission of a region that is consistent with the geographic boundaries of a state planning region shall offer an ex officio, nonvoting membership on the governing body to a member of the legislature who represents a district located wholly or partly in the region of the commission.