Quick Question: Is there a specific SDK (python 3) for NSX-V (6.4.x? I know there is one for NSX-T (version 2.5.1)?
it depends but you need to check release notes or docs from both, for example for V:
GitHub - vmware/vsphere-automation-sdk-python: Python samples, language bindings, and API reference ...
https://code.vmware.com/web/sdk/2.5.1/nsx-t-python