care to elaborate what was the problem with the separtate user account?
I have no experience with NP/QS just NP/QV but the requirements worked for me. And I learned the hard way that you need to follow them. Else you are able to install the server and all parts but you can run into problems later (own experience).
We have used two separate LOCAL ADMIN accounts to install QS and NPrinting, but have to re-arrange the respecful services to run under the same DOMAIN account at the end. This was the only way in our case to make the NP Connectors working with QS applications. Otherwise the connector just failed to work.
Tried it on both QS 3.2 and Sept 2017 releases along with NP 17.2 and Sept 2017...
I am not sure if this is a part of the same problem, but the new feature (a "Connector's Validation") in "Sept 2017" only works if initiated by Domain account....
No Section Access or other authentication restrictions were applied to any of the applications.