No, it is not correct to say that NPrinting 17.3 will only work with Qlik Sense. If you look at this link: System requirements for Qlik NPrinting Engine ‒ Qlik NPrinting you will see the supported configurations. You can use the NPrinting Engine with QlikView 11.20 SR15+.
I don't know for sure that the Dynamic Variables in email has the same functionality as it had in NPrinting 16. But I think that somebody else can tell that.
If you are already using NPrinting 17. I would suggest, and somebody correct me if i'm wrong, that you update to the latest version of NP 17. Beware of the update procedure. You need to do it in steps. Take a look here: Upgrading Qlik NPrinting ‒ Qlik NPrinting