This is kind of fiddling in the margins though; I'm having a lot of difficulty determining the semantically-correct way to get Qt not to funnel all activity through a single thread.
Specifically: there's no way to guarantee no overbuffering due to the startup race, other than having QAudioOutput obtain data by pull rather than push. But if it's pulling then that implies an extra buffer. And since the sizes it may pull are not explicit, there's guesswork involved there.
So: no extra buffer => uncontrollable risk of over-buffering. Extra buffer => a controllable risk of over-buffering.
