The form of government provided in this chapter shall be known as the "charter" form. A charter form of government shall be established by a written charter approved by a majority of the electors of the county as provided in this chapter. The charter form as provided in this chapter shall be an authorized optional form of county government within the meaning of article XVIII, section 12 of the Idaho Constitution, and shall be authorized in addition to those optional forms provided in chapters 50 through 57, title 31, Idaho Code. Unless provided otherwise in this chapter, the provisions of the optional forms of county government act shall apply to this chapter.