Mayor-Council: The mayor-council plan incorporates a clear separation of powers between the executive branch (the mayor) and the legislative branch (the council). The city council may: enact ordinances; levy taxes: adopt a budget; and set compensation, in addition to other legislative duties. The mayor serves as the chief executive and administrative officer of the city and oversees the management of the city's daily affairs (See KRS 83A.130). He or she serves no legislative function and may only vote in order to break a tie, unless such a tie-breaking vote is prohibited by a specific statute. KRS 83A.130(5).
Commission: The commission plan consists of a mayor and four elected city commissioners who together comprise the city commission. The members of this commission share legislative, executive, and administrative authority in the city. Thus, the commission plan does not have the strict separation of powers of the mayor-council plan. The mayor acts as a voting member of the commission, with only limited responsibilities and authorities as mayor, such as presiding at commission meetings and executing contracts. Although the ultimate authority is vested in the city commission as a body, KRS 83A.140(6) requires that administrative functions of the city be separated into departments by ordinance. Each of these departments is placed under the supervision of one of the city commissioners, unless the commission has created the office of city administrative officer. The commission as a whole is free to override any action taken by a commissioner overseeing a department. If there is a city administrative officer, that person may be delegated the supervisory authority over the departments.
Manager: The city manager plan is similar to the commission plan in that it provides for a mayor and four commissioners who make up the board of commissioners. The distinction is that significant administrative powers are vested in the city manager, which is a position the board of commissioners must establish (See KRS 83A.150). The manager is appointed to serve an indefinite term by a majority vote of the board and is responsible for the supervision of all departments of city government and the conduct of city employees. As in the commission plan, the mayor is a fully functioning member of the board of commissioners with only a limited role as mayor.
More information on this topic can be found in the City Officials Legal Handbook.