You need to match the artifact name to the artifact ID if your game is published on the Epic Games Store. The OnlineSubsystemEOS plugin will read the artifact id passed by the Epic Games Launcher via the -EpicApp CLI parameter and match it with an artifact name in config.
If you’re not planning to launch on the Epic Games Store, the artifact name can be any string you want. You don’t need to pay the EGS fee to use EOS on another platform.