From what I see on the demo, I can either have product categories or the grid layout…

The problem I see is that once you click on a category, you don't have the list of other categories visible any longer.  It seems easy to get lost in the store.  I have over 250 products which won't work in a grid format and definitely needs lots of categories and sub-categories.

Am I missing something, or am I correct that the categories are not always displayed?

Can you have grid layout with categories too?