I think the limits, when it comes to timing, depends on the play routine. Normally a player would run once each frame (60 times per second on NTSC). If you recorded freely with a DAW, you'd likely notice some artefacts if you were to quantize stuff to 60 Hz ticks.
While they usually are in practice, players aren't necessarily limited to 60 Hz, though. You could have several ticks per screen redraw to increase the resolution, (probably) use a timer interrupt to advance the ticks at an arbitrary rate or so. The only real limit is how much time is spent on each tick in the play routine, which in most cases should be less of a worry to you than MIDI jitter.
If you are tracking and want to make things sound more natural, have a look at the note delay/cut commands. Some trackers will even let you record MIDI freely and insert the delay commands for you as you play.