All H9000 latency information can be found here: https://cdn.eventideaudio.com/manuals/h9000/2.0/content/setup/DAWLatencyCompensation.html
I am not sure what the issue you are having with the Cubase External FX latency measurement. You should first configure your FX Chain on the H9000, then bypass all of the algorithms, and then trigger the measurement from Cubase to measure the latency of the FX Chain.
There shouldn’t be a noticeable amount of latency when you use a Direct I/O connection to patch the analog inputs to the digital or MADI outputs for tracking.
I would suggest using the RME software to monitor your inputs before you get to the DAW when tracking and that should give you minimal latency.