I think the local user number is fine to be 0, since they will both be local clients when loading into the entryMap. That simulates the start screen of their device. They would need unique controllers when in the lobby, which is the OSS Session map. It seems that the project is already setup like that.
I, too, am having trouble figuring out how to use multiple users to test in Unreal PIE. Both clients have the same Oculus identity.