FWIW I noticed the Coolbits xorg.config option today and tried it out. It enables a "Clock Frequency" menu in nvidia-settings, meant for overclocking but of course you can also use it to manually set the clock frequency to values inside the spec.
Initially it seemed to have some effect, but after some more thorough testing that seemed more like an illusion. Even if I use that menu to set the frequencies to something ridiculously low, the fps rate doesn't change.
Maybe I forgot one step or so though, someone else may be more patient and lucky.