Does that mean we don't even need Mellanox ML2 mechanism driver and corresponding SRIOV agent ? If so, can we just plug in an Intel card that supports SRIOV without needing any Intel specific driver/plugin?
Yes, in Juno for a basic SRIOV setup, you don't need a vendor-specific mechanism driver. I have tested the inbox support for SRIOV in Juno and it seems to work well.