If your idea for interconnection and migration to the private cloud involves using NSX and L2VPN so that you can “stretch the vlan” between your NSX private farm and the one into the Cloud you are doing it wrong.
No matter if you are using VXLAN as a transport or any other technology, if your plan involves layer 2 extension you are doing it wrong.
Not every application should be migrated to the public cloud, and most definitely you should not migrate something that relies on a layer 2 adjacency to work.
If layer 2 extension is a way to allow ip mobility, then again, it’s just a lazy design. There are better ways to provide same-subnet IP mobility that doesn’t require layer 2 (see LISP or BGP-EVPN Type 5 routing for example).
Even if it works on Power Point or on a small demo, you really should NOT.