the profile can be manually activated multiple times on different devices. However, regarding autoconnect, the profile will autoconnect only if it is currently not connected otherwise.
the profile can autoactivate and be manually activated multiple times together.
the connection profile can only be active once at each moment. Activating a profile that is already active, will first deactivate it.
indicates that the per-connection setting is unspecified. In this case, it will fallback to the default value, which is %NM_CONNECTION_MULTI_CONNECT_SINGLE.