Is it necessary to create for each store a new project?

We recommend including all stores in one project. 

If you have one project for all stores, you can then share the same template for hundreds of stores and you don't have to create a new planogram for each store. At the same time, you will have all planograms in one place and you can quickly see in the project, for example, which stores (and which planograms) contain a given product and so on.