You're getting all the layouts you see in the demo. The theme comes with importable demo content. You'll just have to replace the images and content with yours and that's really easy to do using drag-n-drop Page Builder.
Nowadays is optimized for the best performance. PageSpeed score is 97. YSlow score is 92.
You can create fully custom pages by mixing and matching the elements available in the theme. You're not limited to what you see in the demo, those are just a few example meant to show you the possibilities and help you get started.
Theme settings are global which means it will be applied to whole site. Some of these options can be changed for each page separately in page settings.