Is it possible to control a PWM computer fan with a resistor? If yes, how?
When a PWM fan doesn’t have a chop signal being fed to it, it functions exactly like a 3-wire fan.

So, sure, try the resistor drop. Not guaranteeing it will work but it’s worth a shot. It won’t damage the fan in any event. It may cause your GPU to overheat though, so use with caution.

Your motherboard may have spare fan plugs that do have PWM control that you can set with your BIOS. If you have a spare that could drive your GPU fans.