range hood exhaust fan?

I installed a 6" computer fan and it is very quiet now. Make sure that the one you get is 12 volts.

OK, I can definitely replace the fan blade and run the PWM controller.
How about these?
https://www.amazon.com/Controller-Motor-Speed-Pump-Blower/dp/B075FN4H37/ref=sr_1_6?crid=12YDMCUP1AICP&keywords=pwm+fan+controller+12v&qid=1637776370&sprefix=pwm+fan+controller%2Caps%2C216&sr=8-6

https://www.amazon.com/Wadoy-D-Bore-D-bore-Replacement-Ventline/dp/B07V687K5B/ref=sr_1_25?keywords=replacement+fan+blade+for+RV+range+hood&qid=1637776613&sr=8-25

This is what's on there.
https://www.amazon.com/Motor-Blade-Kit-Range-Hood/dp/B004882JOA/ref=sr_1_33?keywords=replacement+fan+blade+for+RV+range+hood&qid=1637776690&sr=8-33

Fans will be always noisy.
Observe that high-end household hoods use blowers instead. Those are much quieter, but rebuilding factory hood to accommodate blower would make whole project.

YES, adding a PWM controller is about the best for reducing fan speed & noise and still maintain enough air flow to evacuate. I replaced our 18 year old motor and blade which was slightly quieter but it was adding the variable speed controller that made it not so atrocious.

Noise is a combination of motor, fan blades and exhaust chamber. The shape and size of the fan blades is typically the biggest factor. Maybe look at a variable speed control for your current motor?