First question was answered somewhat,here's the scenario,remodeling bathroom,ran 20 amp service,wired in fan/light .light is wired for use by itself.Fan,light in tub,shower,vanity light and three outlets [one outlet is gfci,20 amp rating. Would like to use 15 amp switch for general light,this is in fan in center of room.Also would like too use 15 amp outlets in other two locations.Is this a possibility?

Since the load on the switches cannot exceed 15 amp, then this is fine to use the 15 a switches.

Same for the 15 amp receptacles, can be used on 20 amp circuits.

Is the shower light GFI protected? Check the manufacturers instructions , may be necessary to GFI protect the shower light, seems like sound advice also, wet shower and a metal light fixture.

The shower light is recesed,new install with proper sealed cover,and yes this light is protected.also there was concern about being in the dark.The fan light in room ceter is on its own circuit and will not go out if gfci is tripped.thanks for saving me some,enabling me too use previosly purchased 15 amp units.