With an etsy style site, where should the shop categories go?

Hi

When setting up an etsy style marketplace, should shop categories be added to the template website? Will this mean those categories will be available to all shop owners and they will work in the global products page? (despite each site having it’s own individual checkout).

I don’t want to give store owners a free rein to create their own categories, but I do want to be able to add to the categories myself at a later date if a client requests a certain one. Assuming the above is correct, will editing the template sites categories lead to changes in each and every store on my network, even if that store was created before the template site was updated?

Thanks

Sally