In addition to the above, I have noticed a considerable amount of (mechanical) 'end float' in modern fans, which can contribute to noise, particularly if accompanied by a lack of lubrication.

A fan has a shaft, with the blades mounted on it. Unless the bearings are completely gone, you won't feel play in the bearings. But the shaft can move into and out of each bearing a bit. That's end float in mechanical lingo, and not great news. Oil helps, even cooking oil from your kitchen.

Yes and No.

As bearings wear fans make more noise. Fans running at higher speeds make more noise. Fans that are not mounted with noise dampening make more noise than those that are sound isolated. Some fan designs make more noise than other designs. All these contribute to fan noise and most can be controlled easily.

end float - This is normal and when power is applied the fan moves axially to center in the magnetic field that rotates it. This is by design.

Oil - It is almost impossible to even get to the fan shaft on most fans in computers, so oil would likely go where it is not wanted. Also, most oils will congeal over time with heat and exposure to air so that would become an issue in the future. Modern fans used in computers in the last 30 years use permanently lubricated bearings so oil is not required.
I NEVER try to lubricate fans in my computer, but instead replace them since they are relatively inexpensive. That said, I also try to make sure I use ball bearing fans instead of sleeve bearing fans. They last a LOT longer with no problems.

The OP changed the software controlling his video card so the fans are not running at max speed constantly which reduced his noise.