Here are some interesting resources I found when I just some weeks ago posted the very same question here, see Example repo for state-of-the-art SSR in Meteor? 
Boilerplates
- GitHub - timothyarmes/ta-meteor-apollo-starter-kit: Meteor 1.8, Apollo 2, React 16, Multilingual ready, PWA, Styled-Components boilerplate (referenced in this thread: Starter Kit with Meteor 1.8, Apollo 2, React 16, Multilingual support, PWA, SSR, Authentication & Styled-Components). This helped me a lot to see in practice how things work.
- GitHub - CaptainN/meteor-react-starter: A starter project on Meteor with React (another good boilerplate with lots of other stuff)
Articles
- Server-side rendering (SSR) in Meteor | by Julian Ćwirko | Meteor Blog
- https://www.chrisvisser.io/meteor/how-to-set-up-meteor-react-with-ssr
Good tutorial on the basics of SSR with React (not related to Meteor):