Thanks for updating the thread.
Let me try to clear your some of your confusion.
X Theme and Cornerstone: In X Theme to design a page you need to use Cornerstone page builder tool. Although when you install X Theme, Cornerstone get automatically installed but it's a plugin. And similar to any WordPress plugins, you can perform all the basic functions like, update, activate, deactivate, delete.
Pro Theme: In Pro Theme Cornerstone is inbuilt into the framework (when using Pro Theme we call it content builder). You don't have to install anything. Just install Pro Theme and in click Edit with Pro button in pages/post.
Hope that helps.