OK, I am not a member of IATF but having done this for a living since before the sorry birth of QS9000 I believe that I'm on firm ground.
1. Up to and including ISO TS 16949-2009, the standard included the verbatim text of ISO 9001 and additional requirements, of two general sorts: one are entirely independent additions; others are specific interpretations of ISO 9001 requirements. For example, TS requires that preventive maintenance include "predictive maintenance techniques"; this is an independent requirement. In a different situation, ISO 9001 demands internal auditing, but TS prescribes several specific formats for internal audits -- specific details on HOW the ISO 9001 requirement must be addressed in automotive.
2. The IATF 16949:2016 will continue this logical scheme; they've said so.
3. If you build a 16949 compliant system, it will automatically comply
with ISO 9001.
4. There is no such thing as a 16949 system that doesn't include ISO 9001. HOWEVER...
5. The REGISTRATION PROCESS is separate, so not all ISO TS 16949 registrations automatically result in an ISO 9001 certificate. One of the registrars I work with charges extra for an ISO 9001 cert; others probably do as well. At the very least, the registrar wants to charge for the "royalty" assessed by their certifying bodies; and they may have different details for their auditing process.
6. If your organization is 100% automotive OEM production, you can stop here... no further worries.
It is hard to imagine why you would care about a separate ISO 9001 cert if you have a TS cert. And, I have one employer who has 80% non-automotive OEM products, 20% automotive OEM; the
TS certificate covers the whole thing, because they use the same management system for all the business, and the products and manufacturing processes are technically similar. All of our non-automotive customers gladly accept our TS cert.
7. It can get more complex if you have a mix of automotive and non-automotive business; the TS scope may not cover your non-automotive business if it is significantly different in character from your automotive business. Say, different divisions with different types of production processes and products. In such a case you might need a separate ISO 9001 cert, if your customers on the non automotive side are finicky.
This might happen, if, say, you make wiring harnesses for both automotive and medical devices.
8. But, NEITHER OF THESE DOCUMENTS are SYSTEMS!!! You will build a management system for your company. Auditors will use ISO 9001 and TS documents, and the associated registration audit mechanisms, as measures of whether the management system you have built meets certain standards.
And, if you're like many companies, your management system will handle other things, too... like environmental, safety, and other requirements.
This whole discussion is unfortunately abstract... but in the end it's not that hard...