There are several ways of setting up a Qu & an SQ together, including a digital connection so that they can use each other’s inputs & outputs.
However for what you want, a simple analogue feed (or several) to the Qu, and a scene that passes audio that to the speakers would keep things simple for the volunteers.
The Apps are different, though feel similar in many ways. Obviously for the Qu-SB, it needs to be able to control everything, as that’s all you’ve got. For the SQ, it’s currently only capable of controlling some of the features.