After loads of research and testing down the sync rabbit hole, I (just last night) found that the Ableton manual is incorrect about setting up audio interfaces. I notified support through an open ticket
The error is here:
https://help.ableton.com/hc/en-us/artic ... -Interface.
"5. On Mac, you can choose separate devices for both input and output, or you can choose to deactivate one of them (set to "No Device"):"
While it "works", you will never ever get stable Driver Error Compensation timing. Every time the Ableton audio engine reloads, you'll get a different offset to use in the Driver Error Compensation box.
In order to obtain Core Audio timing and synchronization with multiple audio devices, you would need to create an aggregate device with all inputs and outputs you plan to use, and use it for both the Input AND Output device.
Otherwise, your recordings will go out of sync the next time you load the audio engine. You can test it by turning Core Audio to None and then back to Core Audio and re-running the Driver Error Compensation test in Ableton Lessons. The delay time will be wrong because the I/O is decoupled. The only way for it to be coupled is to use the same device for input and output.