What I was looking for is actually a way to authenticate and authorize communication between nodes regardless of user.
For inter node communication, for my case at least this is what was needed:

<clickhouse>
  <interserver_secret>clickhousecluster</interserver_secret>

  <remote_servers>
    ...
  </remote_servers>
</clickhouse>

When this is setup and no user/pass or secret is provided within <remote_servers> clickhouse uses the standard RBAC.