Site template - Customize home page

Hello, I create via a power automate and a JSON script a team site in which I add a new library with specific fields.

However, I can't understand what the "SiteDeignID" line (in Power Automate, see below) is for because the values I put have no impact on the creation of the site.

My goal is to create a site template with specific libraries (which I manage to do) but I would also like to be able to configure the home page by removing the basic webparts (see below) and adding the ones I want (which I can not do).

I don't want the actuality webpart neither activity webpart. 

I think it's not possible to make these changes with the JSON script. 

Thanks !