Nuendo and Avid HDX

Hello, due to some Pro Tools terrible bugs that I cannot work with, I’m switching to Nuendo that I got with a good xgrade option from cubase. I own the 11 license but I’m running the 10 because I am on mac OS HS and Nuendo 11 requires Mojave.
Then, in VST Audio System I set Avid HDX, then tried to reduce the latency by lowering the buffer into the HDX Control Panel. By changing the buffer the latency changes accordingly down to 256 samples, but trying to go below this value it seems that nothing change and I am unable to get less than 11.61 in and 11.61 out ms. Too much for recording. Is there anyone who uses Nuendo/Cubase with the same my setup?
Thank you