A proposal for combining appointive offices of two or more counties, appointive offices of a county and another political subdivision, or appointive offices of two or more political subdivisions which are not counties may be implemented through the execution of a joint    powers agreement, unless a specific procedure for combining particular appointive offices is otherwise provided by law. The proposal is not subject to the referendum or election procedures of this chapter. A proposal for combining both elective and appointive offices of two or more counties, between a county and another political subdivision, or between two or more political subdivisions which are not counties, is subject to the referendum procedures of this chapter only in the county or other political subdivision of the elective office.