No form or plan of insurance covering any group or combination of persons or risks shall be written or delivered within or outside this state to cover persons or risks in this state at any preferred rate or on any form other than as offered to persons not in such group or combination and to the public generally unless such form, plan of insurance, and the rates or premiums to be charged therefor have been submitted to and approved by the commissioner as being not unfairly discriminatory and as not otherwise being in conflict with subsection (1) above or with any provision of parts 1 through 4 of chapter 16 to the extent that parts 1 through 4 are, by their terms, applicable thereto.