The camera and mic settings have changed in the moderator settings because others have this same concern. 
As far as asking for camera and mic permissions when would be best in your opinion. After one has entered a room.  

 I think it could ask for the microphone only and when get into the room it starts closed, even because can disrupt the talk, the camera permission would be better only after pressing the camera button imo. 

 Ok got it. I will add this to the list.