Minimising latency while recording/monitoring audio - Cubase 8

[alligatorlizard]

Just been reading up on this, I know there are lots of posts already on latency, but a few things I couldn't totally clarify:

1) The "adjust for record latency" option is not explained or even mentioned in the manual... As I understand from other threads, this is for when recording midi - if there is any latency, there will be a tendency to "play ahead" - in which case the midi notes will end up placed on the piano roll earlier than intended. So this option compensates for that, effectively placing the midi notes on the piano roll at the moment when you're hearing the notes from the monitors (eg after latency), not the moment when the midi key/pad is actually struck. Presuming I've understood this correctly(?), is this only relevant for midi recording or does it have any application whatsoever when it comes to audio?

2) Right now I'm recording direct input guitars - it's nice to monitor thru cubase, as then I can hear the Guitar Rig amp sound etc as I play. However, even with low buffer settings, I find it hard to record dead in time - after all, am I timing the physical impact of pick and guitar string, or the monitored audio, which is however-many ms later due to latency? Obviously reducing buffer size and using "constrain delay compensation" helps, but if I want absolutely no latency I use direct monitoring (ie thru my Fireface 400 mixer) - sucks to have to record a distorted guitar part completely clean, but at least the timing is going to be right! Or is it... are there any other parameters I need to adjust to make sure direct monitoring eliminates recording latency?

3) There is one other parameter I adjusted, the "record shift" value, which I've always left at 0 in the past. To determine how to set this, I activated the click, and then recorded it back into cubase. Zooming in on the audio wave-image, it seemed to be roughly 3 or 4 ms after the beat (or around 200 samples). So, I've entered a value of 200 samples in the "record shift" box - did the test again, and the recorded click was now dead on the beat. Presumably the initial latency here was just the inherent soundcard/system latency, and as there's no way to eliminate this, cubase gives you the option to manually compensate - have I understood this correctly? And with this done - and while using direct monitoring - is there any reason why my guitar part shouldn't now record with no latency whatsoever? eg when playing it back, I should hear it in exactly the same relationship to the rest of the track, timing-wise, as I heard when I played it in?

I know there's a lot of questions here, but any advice much appreciated!