I watched Digital Foundry's video on the PS5 version (they didn't get early codes, which kinda tells me something) and it looks like the general thing for console is you're honestly better off playing at the 30 FPS mode as it stays stable most of the time (the biggest issue is areas with bodies of water with ray traced reflections), while 60 FPS is only stable in smaller areas and dungeons, the more open spots seem to stay around 40-something, and resolution dipping to sub 720p (and for a PS5 game that's quite the "accomplishment," this is more of what I'd expect from a Switch port that was either "far too ambitious for its own good" or "was ported by a bad team").
It looks to me the biggest issue is the devs likely didn't properly optimize the game's use of raytracing, and the fact it's always forced on, even in "performance mode," is one of the big issues as I bet if you could turn it off and use the "less impressive but also way less taxing" screen space reflections instead the framerate would be far more stable in 60 FPS mode.