from what ive heard, angels show themselves as you believe them to be. for example, if you believe they look like squirrels, then they will manifest themselves as suirrels. and for people who believe that angels are those winged beings with white sheets on, they will show up looking like that. i have heard though that angels have manifested themselves as orbs (not small spirit orbs) and that they look like a bright unnatural fire. maybe an orb is their true form and they only show their true form when the person they are encountering dosent really believe in angels, or dosent have any exact belief in what they look like. if youve ever watched harry potter and the prisoner of azkaban, and you remember the scene where they have the boggart in the wardrobe that turns into what people fear the most, you have an idea what im talking about. angels kind of act like boggarts (form harry potter of course).