Looking into this further and it seems that AUX I/O does not use latency compensation and also adds additional buffering on the inputs/outputs: https://avidtech.my.salesforce-sites.com/pkb/articles/faq/Auxiliary-IO-Frequently-Asked-Questions

The H9000 itself does not introduce much latency, you can find the latency specs here: https://cdn.eventideaudio.com/manuals/h9000/2.2.11/content/setup/DAWLatencyCompensation.html

I assume that this extra latency introduce would be an issue with any USB Device being used with AUX I/O.

Fixing the USB clock error on the H9000 is not difficult, instructions to do that can be found here: https://cdn.eventideaudio.com/manuals/h9000/2.2.11/content/setup/usbsetup.html#changing-the-usb-audio-sample-rate

The clock error will be resolved by toggling the sample rate of the H9000 USB audio device or the aggregate device in the Audio MIDI setup settings on your Mac.

I would also suggest that you may be better off using the analog/digital protocols on the H9000, or investing in the PTHD card for the H9000 to integrate it into your HDX setup.

There are many ways that the H9000 can work in any setup, I’d be happy to help provide further suggestions/instructions if you can let me know what your rig consists of and how you’d like to use the H9000.