A1 sight aperture - sight holes are the same size just located at different heights.
A2 sight aperture sight holes are DIFFERENT sizes (smaller one is cupped to attempt to make a poor man's hooded sight). Apertues are slighly offset in height (should be 2-3moa but it can vary).
Match sights generally have apertures which can be changed and screw-in hoods are available.
Yes the Match apertures can be used on the A1 sight assemblies (they all use the same threading).