Complicated. You need programing to send start / slices messages before note.
There is a latency, time needed before the start / slice change.
Less latency with start points, around 17/20ms.
Up to 60ms with slices (possibly reduced with odd midi values)
Triggering slices with midi notes? - #195 by sezare56
If you control the crossfader assigned to start / slices, no latency. But in that case, you have same crossfader value for all tracks, hence same start / slice value.
I’d rather use a launchpad pro.
Check this long thread.
What is mlr?