I think graphic mode should be the default mode on PS4 Pro. There are very few FPS drops and only in cinematic moments like supers and cinematic danger zones. That also happens in regular PS4 version.
Graphic mode should be 2k.
I'm just talking to John, who made the Digital Foundry video, over on Resetera and he even has the suspicion that the game is not PS4 Pro enhanced at all. If there's dynamic res enabled it would automatically display the game in higher resolution on PS4 Pro performance mode, and it would make sense that PS4 Pro's graphics mode is just PS4's graphics mode only in stable 60fps.
I had a suspicion too that the game was actually not enhanced at all, and I mentioned it in here before. Shame on Team Ninja if that is actually true.