React's website is a great place to start looking if you need more info. Thinking in React is specially good if you're not very familiar with it: https://reactjs.org/docs/getting-started.html#thinking-in-react (from this link you can go through to the actual post).
The simplest way I can see to link SS data into React is to either use GraphQL or a JSON string that React can access once the page has rendered. eg, somewhere on your template have:
- var data = Page.toMap();
Your React components would be defined and compiled from JS files (eg
Header.js exports a
Header component). That JS is only ever run in the browser, where the template variables from SS will already have been resolved into their values.