Hello

Is there a particular reason you want to use nParticles? I imagine just using nCloth to have the leaves fall would be a less complicated way to go about this. You could set up a few leaves to fall how you want them to and save them as an alembic cache that you can later import and manipulate/offset to give the impression of having more leaves if that's what you needed.

Or, you maybe could instance an alembic cache of a leaf onto the nParticles?