Regarding ACI and vCD, I have just deployed this and there is no integration. We just need to import the networks pushed down by ACI as external networks into vCD.
I did have to deploy and configure a NSX Manager instance but didn't prep any clusters for NSX. It just needs to be associated with a vCenter before you can add a vCenter instance as a resource provider for a pVDC.
Apart from that, I'm not sure what you really mean by the following comment.
have a use case for vCD, but NSX is a dagger
