Years ago someone asked the same question. The answer at the time was that JUCE autoselects the best format for the relevant audio device. There’s still no setBitDepth.
I know my external usb dac/amp works with 24 bit data at best, but if I recall from some ALSA experimentation it ‘accepts’ 32bit floats, which means the truncating would happen somehow (I’d rather do it myself) or there’d be unnecessary downconversion. What does JUCE do here and what should I?