More information needed.
Update your post to include full system specs and OS information.
Make and model GPU? Other case fans? Arrangement?
PSU: make, model, wattage, age, condition?
Try to describe or even record the loud noise and post accordingly.
Buzz, hum, rattle, whine....? Do you feel vibrations?
Could be just some resonance due to loosening screws and connections.
What to do:
Power down, unplug, open the case.
Clean out dust and debris.
Ensure that all connectors, cards, RAM, and jumpers are fully and firmly in place.
No loose cables/wires hanging about.
Check that all screws are snug and secure - do not over tighten.
Key is to identify the true problem.
Forgot to mention, sorry. The Galax support, while under warranty. It was replaced in January '21Regarding: "It already happened once in the past, not sure if they replaced the fans or did just a clean up ".
Who is "they"? How long ago?
In any case, I suggest that you take the computer back to them again. If you do things on your own then, best case, that may violate any existing warranties.
Worst case - you break something and likewise will have no warranty.
Could you recommend an AIO for GPUs or is not worth it?You may be able to do some fix or replacement yourself.
However, the key is to determine the source and cause of the noise.
Nothing may need to be fixed or replaced. Could be resonance or vibration both of which can result from certain combinations of fans and fan RPMs.
For example: At low speeds the fan may be just slightly touching something or able to move just a little bit. But then, at a higher speed the fan may no longer able to move and no longer touch.
All sorts of variables and forces involved.
If you can discover some way or some set of circumstances where you can make the noise start and stop then you will likely identify the culprit(s).