I will say, so far at least, it's performance on PS5 is certainly better than the original on PS4, which is where I experienced that game. Also there's still some noticeable pop-in in both modes, particularly the icebergs. There's definitely some tearing when in Performance mode as well. I'm not sure on the specifics, but it seems like 'Performance' targets 1080P60, while 'Quality' targets 4K30.
I'm kind of surprised how not great the performance is on PS5, even when set to 'high framerate' mode. Maybe if I was playing this first rather than after Subnautica I'd feel a bit different.
about 3 hours? I've enjoyed it so far, though it hasn't quite hooked me right away like the first game did. Started playing on PS5 as soon as it unlocked last night.