I'm a front-end dev, learn now React, really like.
It is better to learn after a front-end-a, Node.js or PHP??
Type already know all about the frontend? How to write in React? How to configure webpack? When using webpack and when rollup? What babel plug-ins/presets to use and how to configurate? As the application architecture to define, then to sleep at night? When it is necessary to make the logic in the middleware/saga, but when a thunk? How to keep SOLID in frontend development? The ecosystem also all probably mastered? now/Next/SSR/CRA?
I've been in the web field 6+ years of spinning, of which the last 2 to React. And I still ask some of these questions. Of course, there are good working practices derived from personal experience and/or experience of colleagues, but these issues arise still
Then decide for yourself. Either is fine in frontend sort it out still, or drive in and jump on the back.
Salary - I don't think there is a big difference. A friend of mine gets $3000+ (purely React and nothing more) all the time and gets offers for more salary jobs.