In reply to Tony.

So, if I understand correct "VXLAN BGP EVPN to OTV Interoperability” is just simplification of configuration legacy approach with OTV-on-Stick.
But new approach introduce much more caveats than advantages at the moment.
In the end it is much more efficient to buy a pair new 9k switches just for border-leaf role and use all this great feature like EVPN Multi-Site etc.