ok....it took me a while to sort out midi issues with nuedo as well. I hard to do a lot of homework to get EZ Drummer, my Axiom controller, and Nuendo to talk to "play nice".
So, to start with, a few questions: are your audio tracks playing out of time with the metronome when you play them back or is it just midi tracks?
I'm not sure of what your understanding of quantizing is, so don't be offended if I'm teaching grandma how to suck eggs...but first, input quantize is also usually "on" by default, so it will "correct" whatever you play to align with it's settings. The quantize function needs to be (a) either turned off to purely hear exactly what you play, or (b) at an appropriate setting for what you need it correct (e.g. quarter notes, sixteenth notes, 64ths, etc). That's probably the best starting point.
Now if you know you're definitely experiencing latency issues (early or late delays), there are unfortunately a lot of things that may cause this. Try searching over at the forums on steinberg's official site as there is a lot of threads on midi latency issues. Both the same problems exist in Cubase and Nuendo so try Cubase first, as there's more users on there.
