A borough adopting a manager plan may, on agreement with a city in the borough, provide that the manager of the city serve also as borough manager. A city adopting a manager plan may, on agreement with the borough in which it is located, provide that the manager of the borough serve also as city manager. Appointment and service of the manager shall be as provided in AS 29.20.490 - 29.20.500. Nothing in this section affects the authority of the governing body to provide for other dual officeholding if the dual offices held are compatible, or otherwise to appoint officials and employees in accordance with law.