In Terms of Policing Within occupied territory more often than not there was a use of local's to police the population around their area under German command. Local collaborators would be given uniforms that resemble that of the Germans and carry out like a paramilitary police force. These collaborators could expect special treatment from the occupying Germans. However when the war swayed in favor to the allies, these groups met their fates by being shamed, killed, ect.

I can't for the life of me remember the one group in the Netherlands I would like to use as an example, so if someone knows the local collaboration group's name that would be great.

As far as the Orpo and German designated Police Forces, They were entwined with the einsatzgruppen where they followed behind the front lines. All though the main focus usually sways to the Einsatzgruppen as the "Death Squads" and being the prime movers, The Orpo were battalionized to supplement the small numbers of Einsatzgruppen and carry out larger scale events.