Your best source for NSX-T multisite is available at NSX-T Multisite Lite
This is considering multi-site topologies, where one single NSX-T manager/control cluster is responsible for more than on site. For other use cases, with separate managers/controllers, they are essentially independent sites that can leverage technologies like L2VPN or HCX, both available with NSX. This might be more adequate for your use case where the DCs seem a bit more distant.
