Permissions and Groups for Node.js

I am looking for the best way to set up Node.js applications on Ubuntu. I set up / var / node / to keep various Node applications the same as / var / www / would.

What I am trying to achieve but seems to be failing:

NodeAdmins (group) has read / write access to / var / node /.

NodeUser (user) has read-only access to / var / node /.

NodeUser is the user account under which Node applications run.

This way, FTP users can modify any files in / var / node / as long as Node applications, when they are running NodeUser, have access to all files.

My questions:

1) Is it correct / safe?

2) How to allow multiple groups to have different permissions on a folder? I used chown to set NodeUser as group owner. I don't believe this is the right way.