Does NodeConfig use ConfigMap internally or they are two different things?
NodeConfig is the Custom Resource Definition (CRD) under Node Operator created by VMWare. According to the VMWare's definition here, NodeConfig is used for the definition in the Node under VMWare's Cloud Platform
ConfigMap is a built-in Kubernetes object for storing the configuration you needed for application.
They are totally two different things in general. CRD is a way to extend the functionality of Kubernetes. There will be a custom controller for reconciliation, in other word, handling the CRUD logic of the resource. You can use your own controller to extend the feature under Kubernetes. In your case, VMWare uses the CRD to let you configure the Node within the cluster.