Craft CMS & React JS Researching this online and not having much luck if anyone has done this before.

How would one get the content from the CMS to update the FE and also create new pages / modules as a normal CMS would allow you to do? 

Little confused on this.
You could take a look at the Element API to help bridge the gap between your React front-end and your Craft back-end. That will at least help you with getting data out of Craft. 

As far as creating new pages and modules you'd use Craft's Control Panel (CP). You're going to have to take a look at the Craft Documentation in particular Sections &amp; Entries.