Which settings should I use to squeeze the absolute most out of Dolphin?

[dannzen]

try internal resolution 3x or 4x with no AA if you gain FPS
but jeah your gpu should handle
3xIR and 9xAA
(auto should scale to 3x with 1920x resolution)

dolphin is not "configurable" like some PC Games...
90% work is done with the CPU Emulation
and you can't change the settings of the Emulation otherwise it wont be a emulation...

so increasing the hardware capabilities is the only choice to get more performance

the other 10%
are some games which are needing a special configuration...
just look into the sticky game threads...
there is everything explained for the specific game