Not sure what the last one really does either.
Through the maxwell BIOS editor we are able to increase to "1.312v". Some people have tested this and report it is less and others have said it does in fact raise the voltage to 1.3v. I am not clear who is right but software monitoring programs will only show 1.275v max
Overclocking Maxwell does seem to be mainly limited by voltage and not quite as straight forward to overclock giving us a challenge