For the 2d you can set your fan low, so as to minimize noise while surfing the internet, etc. Check temps to be sure, but I have mine set to the lowest (25%) and the card temp still stays pretty low.
The "low power" 3d is i think for watching videos, etc. I have my fan set to 25% for that, too.
The performance 3d is the setting that is used while you are gaming. Fan noise is probably less of a concern for you here, so try setting it high, 70-80% or more. This should give you better GPU cooling while gaming. Use speedfan or something to monitor your in-game temps. The default fan settings are 53%, so boosting the performance 3d fan speed should help keep your card cooler
Hope that helps.