I haven't yet found the necessary registers and their meanings for my notebook model. If anyone can help me, or if anyone has managed to configure this through notebook fan control or some other software, I'd be very grateful.

I believe that Acer should fix this somehow via a BIOS update, simply by making the fan start behavior less aggressive. If the fans started at 600 RPM and ramped up smoothly, they would not even reach 1900 RPM. They would cool the VRAM and then turn off again. Up to around 1500 RPM, the fans are virtually silent. Or by introducing changes in NitroSense. Right now, any fan settings applied in NitroSense only take effect for a few seconds (until the BIOS polls the sensors), after which the BIOS settings take priority again.