Are you sure? You have to reboot your PC for the setting to take effect. I ask because this sounds exactly like the issue I had.
With prefer maximum performance (look at the GPU core clock):
With adaptive:
The fact that your load temperatures are in the right range tells me your GPU is at 1000MHz at idle, when it should be much lower. Download Afterburner and check the GPU clock, and you can use this to set a custom fan curve (but you shouldn't need to).