I think you are asking what can ConfigMgr do to an unmanaged machine? i.e. a machine without the ConfigMgr client installed. If I have interpreted your question correctly, it can do discovery (except heartbeat discovery), but not inventory. Inventory requires the configmgr client agent to be installed.
You'll get some basic information depending on the discovery method used https://docs.microsoft.com/en-us/sccm/core/servers/deploy/configure/about-discovery-methods.
I'm not a licensing expert, so please consult with your Microsoft licensing representative about the options available to you.