It depends on what code cycle you are under, if you are in an area under the 99 code it is 125v 15 and 20 amp branch circuits supplying receptacle outlets, 02 and 05 it is 125v 15 and 20 amp branch circuits supplying outlets, this covers all outlets including smoke alarms and lighting.
I agree that the master bath is not required to have AFCI protection.
Roger