I moved your post since it was a new set of questions and this better exposes the answer for others.
Yes, that is how Site Sculptor's/PowerCMS 2's template feature works. You are creating a subpage of the page that you defined as a content management template.
No. In this version of Site Sculptor the navigation is not dynamically updated based on any template pages. This might be added in a future version.
or can you only add sub pages?
In Site Sculptor you could set the Home page as a content management template, and create pages based off of that.
This feature is available in PowerCMS 2 but not in Site Sculptor. One of the reasons for this is that Site Sculptor's CMS is more end-user focused, and providing Add/Delete functionality like this would require a user to have a greater understanding of editing code. Especially since any deleted page would still be linked to in the navigation, and the file itself would still exist.
You can purchase a license of PowerCMS 2 and upgrade Site Sculptor's CMS if you want this functionality.