Here are the results of that test, using only Nuendo and no VST Connect…
Nuendo does indeed know the I/O latency of my RME Multiface soundcard, down to the thousandth of a millisecond. With the buffer set at 4096, I played a single sample impulse out of a single output and physically patched that output to an input of the same soundcard. I recorded this looped through impulse onto different tracks, each using a different buffer setting, all the way down to 32. Every single recording was placed exactly in line with the original source impulse sample. This was the expected behavior.
Here is a screen shot of the test:
I can do the test with VST Connect and change the buffer size on the VST Performer side and the impulse will be further and further off as I increase the buffer size.