I currently try some new stuff. Instead of express I am currently debating between koa and restify. Instead of MongoDB I use RethinkDB.
For the frontend I use angular.
No, I use only one server. But the backend and angular both have their own subdomain. For routing I use Nginx.
So app.domain.io would go to the angular part and backend.domain.io goes to the backend. Also, they don´t run on port 80, they run on a port I can decide.