Actually the wide cabinets are preferable to narrow cabinets for edge diffraction
Not really. Narrow cabinets less than about 5 to 10 inches wide can be very good (smallest is best and this is important in the mids and HF which is why you sometimes see a triangular mid and HF with a woofer box below). 1 to 3 feet is less good (generally manufacturers will place the tweeter off center which helps). A flush wall mount is the best of all as there is no diffraction and ALSO no rear (wall behind speakers) quarter wave cancellation in the bass (below about 400 to 600Hz) Recall that bass radiates omniderectionally whereas MF and HF rediate mostly forwards into a "half-space" - so in order to create the realistic illusion of a point source then you should really try to flushmount in a wall.