I'm sort of ignorant on pros and cons of whether to mount a photo to a board. and if so whether to do that myself of pay for the best place in town to do it - versus any other way of holding it in the frame. I am keen on having a strip of something, either a mat, or if you prefer not a mat, a piece of spacer (they come in bands about four feet long, have a sticky side that faces the frame, not the photo, and keeps the photo from resting on the glass or plexi. I would be keen to keep moisture out of the inner space of the framed photo - perhaps more of a concern by the ocean in northern california - thus securing backing with tape, all acid free yadda yadda.
I've two photos by pros, and they're both matted. Haven't taken them apart to see if they're attached to a backboard.
Thinking, there are also acid free hinge thingies, that you don't see, behind the photo.
Maybe Boomer will be along...