How does voltage and resistance affect an electrolysis?
Voltage determines the kind of chemistry at each electrode.  Gold is purified by plating the anode to the cathode at minimum voltage for the half-reaction, so impurities either do not dissolve and do not plate out.  Copper electrorefining electrode mud contains valuable trace elements in concentrated from.

Current determines the amount of chemistry, ~96,500 coulombs/mole of electrons.

Cell internal resistance converts input energy, power multipleid by time, $\ce{I^2Rt}$, into useless heat.  You then want small electrode spacing and good electrolyte stirring.  You then need enough voltage to do the chemistry, plus more to compensate for resistance losses, but not so much voltage that undesirable chemistries are enabled.  Does cell resistance increase (ohmic) or decrease with temperature?