Does anyone here know of or has used any React + Node starters/boilerplates that come with auth already set up? If not, what is the best way to set up auth for such a project? Is PassportJS my best option?

Yes. PassortJS. You could also use

auth0

https://auth0.com/blog/react-tutorial-building-and-securing-your-first-app/

Funnily enough, I was reading the exact same article right now. 🙂