An individual store may need one discreet diffuser. A chain needs a repeatable fragrance specification and an installation plan for different store sizes. Start with the floor plan, target audience and places where scent will be noticed.
It applies just as much to a single flagship defining a new store concept as to a dealer network wanting every outlet, however small, to feel like the same brand. The strategy differs by scale, but the underlying question is the same: what should this brand smell like, consistently, everywhere it is present.