Does this even happen when sample rate is set to 44’100hz / 16bit?
Ideally the App you are running is at the same sample rate as the Mini / Play+ .
With those settings i haven’t had any issues using AUM on my M1 iPad Pro.
The clicking/distortion you mention, i’ve only seen when connecting and starting things in the wrong order.
I’ve made a video a little while ago with the Play+ regarding this exact issue, but this applies as well to the Mini. Check out this comment for more details:
Hope that helps. 