I have been having the issue recently with an fan in my case being unnecessarily loud. I have two separate fans running and the PC is relatively cool. Side note I don't want to turn off the CPU/GPU fans, only the one in the case.
Safe enough, just disconnect it.
Just so long as your parts do not get overly hot.
What is the make/model of your case, and what is inside that might need airflow for cooling?
Depends. The better option would be to just purchase a new case fan to replace the noisy one.
You can test it for a bit without damaging anything as long as you're monitoring CPU/GPU/MB temps.
Safe enough, just disconnect it.
Just so long as your parts do not get overly hot.
What is the make/model of your case, and what is inside that might need airflow for cooling?