Yes the Audio Buffer size can be changed as can Sample Rate and anything else that normally works, all without the driver.

EDIT:

To further clarify; I normally use the Montage as the input device and an Apogee Audio Interface as the output device in Logic.

However I just disabled the Apogee and used the Montage as the Audio Interface (both input and output) and the result is still the same.

Everything works fine without the driver, including availability of all audio and midi inputs and outputs, all routing configurations that I tried, and both buffer size and sample rate can be changed from within Logic. The changes are all reflected correctly in Apple's Audio Midi Setup App.

I reinstalled the Yamaha Steinberg USB drivers and still have the same issue, Other than that the Montage class-compliance work fine without the Steinberg drivers on My iMac.

So you do not need Yamaha steinberg USB to connect to a computer if it is an OS X macOS Sierra if it is Windows OS then one would probably need Steinberg USB drivers.

I have a windows PC but not interested in using it for Music production.

I may have found the culprit for me loosing bluetooth connectivity for my mouse and keyboard as well as computer freezing if I shut off the Montage while running the Logic Pro app. It only Happen on My iMac pro Late 2015 Retina. It does not happen with My MacBook pro mid 12 or late 15.

The culprit may be Paragon NTFS when I start My iMac pro and the NTFS initiates mounting of the Hard drive I loose my Bluetooth connection to My magic mouse and Keyboard.

This may be the drivers used by Paragon NTFS to access the external hard Drives.

I go to MIDI Audio setup I notice that apple now added Bluetooth/MIDI for ability to you use MIDI over Bluetooth some how because of this there is a compatible issue that conflicting with the USB and Bluetooth and also conflicting with the Yamaha Steinberg USB drivers.

Maybe those who have had this same problem may be using the Paragon NTFS for Mac.

I have submitted a ticket to Paragon raising this concern waiting for a response