Just PS4 Pro at the event I'm afraid, and only with 1080p output selected. Possibly there's more in store with the 4K mode. It'd be unusual if it's ignored entirely.
But yes, X is the one to watch at launch. If it's only 1080p there (small chance), it should be the best at hitting 60fps.
This was a older build also? Was it was still played a on debug Pro?