That depends, hardware and drivers influences the latency. There is not a exact number of buffers that everyone just should use.
Set it as low as your system allows, without it starting to introduce audio artefacts. That number can be different from project to project.
Personally I can get away with a 128 sample buffer and asioguard turned ON for the majority of projects. That gives me a latency around 4ms on my RME device and around 8ms on my Steinberg device.
generally, no you don’t move your part after recording.
just to complicate the whole situation and worry you further.
MIDI has latency AND jitter
MIDI is serial and a MIDI ‘on’ note takes about 1ms to send - so a big jazzy chord will actually be smeared over 6 or 7ms because of MIDI alone.
VST instruments have latency - and sometimes any samples have a bit of ‘air’ in front of them creating more ‘latency’
Lost of D/A convertors add ADDITIONAL latency not reported back to cubase
Sound takes approximately 1ms per 34cm to reach your ears (admittedly not relevant on headphones)
In most instances you automatically allow for this when you play - just as you allow for the natural ‘latency’ in a piano key. 4ms delay is about 1.4 meters - so approx the distance from your ears to the microphone position when micing up a grand piano.
incidentally, trivia fans, I suspect that Cubase/Nuendo still support LTB as part of their MIDI system. The Midex range of interfaces are the only ones that I’m aware of that use it - but theoretically that would reduce, but not eliminate jitter/latency from midi in/out.
LTB/Midex8 was a design from Christoph Kemper, Access Music founder and Virus line designer.
It works very well on older version of Cubase, but on a current system with modern Cubase 8.5+, external MIDI timing seems just marginally better on a Midex than with a regular USB MIDI interface. As a whole, it doesn’t get any tighter compared to early versions back to VST5 & SX…