NX-API has FINALLY made it’s way to another switch platform. The Nexus 3000 was the first switch series to receive the blessings of NX-API outside of the intial 9000 line. There don’t appear to be any differences between the implementations – hopefully there are none. Again, without a published NX-API “standard” it’s hard to tell. For features present on the 3000 series that are not present on the 9000 series, there are likely unique data structures for those features, obviously.
Read more on the Nexus 3000 programmability guide – NX-API was introduced to the Nexus 3000 series starting with NX-OS 6.0(2)U4(1).