Today in vsperf OVS with DPDK VM loopback application is test-pmd and the Vanilla OVS VM loopback application is linux bridge. The VM loopback application for the guest should be configurable from settings/command line parameter.
As well as this Vanilla OVS should be able to use Test-pmd as the VM loopback application as well as Linux bridge. OVS with DPDK should be able to use Linux bridge as well as TestPMD