> Does the new timing model use an audio rate clock source or does it
> use asynchronous timing?
It isn't really a new timing "model" that replaces the old one. It is better to think of it as a higher level interface to timing that calculates tempo-based intervals. So if you set the underlying timing infrastructure to be synchronized with audio processing by enabling Scheduler in Audio Interrupt mode, the tempo-based timing will use it, along with traditional millisecond-based timing you've come to know and trust.