You're always going to get some time lag between realtracks and live recordings, even with buffer sizes as low as possible. The MIDI/latency settings won't help. It's most noticeable when there's only one live track playing against several realtracks - as you build up more live tracks the natural variation in timing masks the effect.
If you've got a problem with one track, you can always got to the start of the track and open the audio edit window. You can then see how late the track is. If you highlight the gap and go to CUT and check the CLOSE GAP box, the audio will slide into place alongside the realtracks.
It's a bit tedious, but it works.