I'm confused as to how it's possible for both platforms to communicate together, both for Node-RED to send data and values to Q-SYS, and the other way around as well.
Well it has an API as it says on the front page. So it is probably possible. I would suggest talking to your account rep about it.
Indeed, it has a REST interface which you can communicate with using the standard HTTP request node.
More information can be found here: