Mold - the shape/geometry of the racquet e.g. beam shape, width, headsize etc. Except for O3 frames (where the O-port holes are done via molding, not drilling) the mold does not have any impact on string pattern since holes are drilled post molding.
Composition - the type of, and in some cases the ratio at which, materials used. E.g. graphite, kevlar etc.
Layup - the way sheets of material are oriented and the angles they are bent at.
Neither has anything to do with drill pattern (drilled after molding) or length (cut after molding).
Using a cooking analogy.
The mold is for example a muffin form - it defines the shape and only shape. For example a form can be shaped like a star. So everything you bake with it will be shaped like a star but can be anything from carrot to chocolate cake.
The composition are the ingredients - so for carrot cake it will be carrots, flour, sugar etc. while chocolate cake will be different because it won't contain carrots but chocolate.
The layup is the order/orientation at which the ingredients are placed in the form.
I highly recommend watching one of the multiple videos showing how racquets are made.