There are no charged particles in OpenMC, it is all photon and neutron Kerma.
I never use heating-local, I believe it pertains to lumping the secondary photons from fission into the Kerma. Though the wording/documentations is a bit fuzzy and implies all photon secondaries.
#3 is the correct way.
It’s to do with how OpenMC accounts for different interactions.
This is a frequent hang-up in OpenMC