I can confirm I have this issue as well with an RTX 3080 Ti. I think it stems from Vsync.
With raytracing and Vsync enabled in the config file, I'm sitting at (a very microstuttery) 72 FPS almost all the time in the realm I have with my friends and I, and very low GPU usage. With Vsync disabled I usually throb between 120 and 180 FPS depending on the reflections, refractions and lighting conditions on screen from the raytracing. I use a 144 Hz 1440p monitor, and it looks like Minecraft is locking to either 144 FPS or 72 FPS. This is extremely annoying and I would prefer if vsync didn't lock to lesser multiples of my refresh rate, especially because having wild swings in framerate like this makes for an incredibly jarring gaming experience. Ridiculously strict Vsync is not something any other modern games exhibit, and a game like Minecraft definitely shouldn't have it either. Now to be clear, I'm not talking about Vsync inherently capping my FPS at 144 (I understand that's how Vsync works), I'm solely referring to how Minecraft is running ONLY either at 72 FPS or 144 FPS. If I'm running under 144, it would be preferable to have Minecraft running at whatever my GPU is putting out and not immediately drop to 72 FPS.
I would just leave Vsync disabled to get around this behavior, but I run into another issue. If I have Vsync disabled, on my other monitor Windows is excruciatingly laggy. YouTube videos are unwatchable because they either lag like crazy or are stuck on a single frame, typing in Discord is hitching and slow, and even the windows themselves lag and hitch if I try moving them around. This behavior doesn't exist with Vsync enabled, nor does it exist in other RTX games or benchmarks that run my GPU at 100%. It's only Minecraft.
All in all, it seems like the terrible performance both in game and in Windows with Vsync disabled via a config file not meant to be found by users stems from a similarly terrible implementation of vsync. Sorry to sound disgruntled here, but I just picked up this RTX 3080 Ti a few days ago and this performance is really disappointing.
Emberstone
I can confirm I have this issue as well with an RTX 3080 Ti. I think it stems from Vsync.
With raytracing and Vsync enabled in the config file, I'm sitting at (a very microstuttery) 72 FPS almost all the time in the realm I have with my friends and I, and very low GPU usage. With Vsync disabled I usually throb between 120 and 180 FPS depending on the reflections, refractions and lighting conditions on screen from the raytracing. I use a 144 Hz 1440p monitor, and it looks like Minecraft is locking to either 144 FPS or 72 FPS. This is extremely annoying and I would prefer if vsync didn't lock to lesser multiples of my refresh rate, especially because having wild swings in framerate like this makes for an incredibly jarring gaming experience. Ridiculously strict Vsync is not something any other modern games exhibit, and a game like Minecraft definitely shouldn't have it either. Now to be clear, I'm not talking about Vsync inherently capping my FPS at 144 (I understand that's how Vsync works), I'm solely referring to how Minecraft is running ONLY either at 72 FPS or 144 FPS. If I'm running under 144, it would be preferable to have Minecraft running at whatever my GPU is putting out and not immediately drop to 72 FPS.
I would just leave Vsync disabled to get around this behavior, but I run into another issue. If I have Vsync disabled, on my other monitor Windows is excruciatingly laggy. YouTube videos are unwatchable because they either lag like crazy or are stuck on a single frame, typing in Discord is hitching and slow, and even the windows themselves lag and hitch if I try moving them around. This behavior doesn't exist with Vsync enabled, nor does it exist in other RTX games or benchmarks that run my GPU at 100%. It's only Minecraft.
All in all, it seems like the terrible performance both in game and in Windows with Vsync disabled via a config file not meant to be found by users stems from a similarly terrible implementation of vsync. Sorry to sound disgruntled here, but I just picked up this RTX 3080 Ti a few days ago and this performance is really disappointing.