Do note that nodebb is a forum platform, not a CMS. I've seen some awful attempts at trying to shovel a CMS into a forum platform in my time. SMF springs to mind.
Integrating NodeBB with a CMS
Is it possible to integrate NodeBB into a cms like keystone, especially sharing the user authentication/management with a cms?
You'd probably have to write an SSO plugin to share authentication. @julian has a ton of SSO plugins that you could use as a sample in writing your own one
As far as user management... somebody was asking for a WP user management plugin. Kind of like if you upgrade a user's privileges in WP, it updates it in NodeBB as well. It's doable but the client didn't end up going for it so we never ended up building it