At the moment I have worked around the FPS problem by installing Minecraft on Ubuntu. Here the FPS are consistently above 100 FPS even with quite advanced graphics settings. I will continue to carry out the tests you have recommended and I will update the post if I can solve it on Windows as well. Thank you all!
By "the FPS drop[s] drastically below 10," I mean that the FPS drops from 130 to a value of 10 or less, causing lag. If the FPS remained at a value of 30 I would be very happy! My monitor has a refresh rate of 144Hz. Thank you
When I start Minecraft I have no other applications running. However I think if it was a resource occupied issue I would see it from Minecraft F3. Instead, as I wrote in my initial post, GPU and RAM workload is relatively low. Even the CPU workload from Windows task manager is under 50%. I've already tried turning off the energy saver mode but I haven't noticed any benefits. It's probably like you say: the problem is that I'm using a notebook.