Structure(s) vs. Categories for product catalog
I find it difficult sometimes to choose between a category group and a structure, so for me it mostly boils down to semantics.

A brand can be both a structure entry and a category. If you're going to have pages with information about the brand/product faily/product, and they will be available in some kind of menu to be browsed by itself, I think I'd go with a structure. If, on the other hand, they are only going to be used for filtering and organizing, a category group feels more appropriate to me.

From what you've described, I think I'd go with:


Products (structure)
Accessories (structure)
Brands (category)
Product family (category)


But as I said, it depends a lot on the specifics of your content.