i am proposing a Cisco ACI solution with APIC and Nexus 9336 Spine switches, can i have the Nexus 3164 as a leaf switch aggregating endpoint groups to the spine switch or must it be a Nexus 9K switch.
No, you cannot. The only supported leaf or spine models are part of the Nexus 9K platform. Please note that not all Nexus 9K models can be part of an ACI fabric. Please reference the latest Nexus 9000 model comparisons to identify ACI support.