Can PerfPRO push workouts up to Garmin Connect?
No, not at this time due to their steep API fees. Use Tapiriik to make that happen.
With Tapiriik, you can push your performances to Strava, TP, or any other site that PerfPRO can push too. You can then set it up so that site then gets pushed to Garmin Connect. As an example, set PerfPRO up to push workouts to Strava. You can then have Tapiriik push your Strava workouts to Garmin Connect and then all is synced up.