High fan speeds are ok as long as the temperature do not exceed the hardware's safe limits. People say for more modern processors anything past 80 degrees C is too hot, even 75 degrees pushing the safe limit of silicon in CPUs and GPUs. I keep my desktop below 80 on the GPU and below 65 on the CPU, but I have poor air circulation for my graphics card and a water-cooled CPU - so this discrepancy is normal.
I have a Zephyrus G laptop and it gets toasty, 75-85 Celsius on the GPU is basically normal when under load in a game or when rendering something.
For you I would recommend downloading something like HW Monitor or HWInfo (one is open source, one is closed source, both do about the same thing). If you see your GPU exceeding 90C I would begin to question the efficacy of your cooling system, or the temperature of the room where the laptop is. Is there sun beating down on it? Are the fans high all the time? Generally as long as temperatures aren't super high (beyond 90 C) you should be fine.
As far as exactly how bad temperatures in the 95-100 C region are, there isn't much data to provide a conclusion more solid than: it's probably not good for you PC, and any higher temperature than 95 C will surely degrade the hardware, and probably cause it to fail faster. And for temperatures above 100 C, your hardware is on the fast track to dying a quick death.