Is there any relation between QAM and streaming?
QAM is a digital modulation scheme. As such it is one way of implementing a physical layer that allows to convey digital information over a given medium. QAM is frequently used in all kinds of systems, including wireless (cf. broadcast TV and yes, also WiFi) as well as wired (Ethernet uses some variations of QAM as well).

What kind of information you convey over this link does not matter to the physical layer. You could send documents, voice, videos, whatever you like, as long as you represent it in digital form. The physical layer does in general not need to know what kind of data is being sent by the application layer.

So yeah, if you want to stream video over some medium, chances are the physical layer uses QAM. If it happens to be an optical fiber, it might not, since optical modulation schemes work a bit differently. But you can view these two things more or less independently from each other.