Q:
cavern of shining lights fps problem
Turning off/tuning down reflections in that cave could help, just in case you didn’t try that yet and just tuned down the general graphics settings without trying separate options.
Since the cave is full of water, steam, rainbows and other lighting effects, and everything gets reflected in said water, that one option alone can eat your FPS alive.
Unfortunately I tried that and turned reflections completely off, for some reason even on the lowest settings for everything the area still runs at 9-10 fps. Thank you for the suggestion though.