Use up to 4 mm² cross-section. The plugs do not look particularly high, but keep, if the wires are soldered to each other very well before. They are quite small and so discreet. I glued the plastic shaft with the cable jacket as additional strain relief. Without wishing to initiate a discussion of whether perhaps soldering is of the devil: Even with high quality Bannanesteckern must either soldering or crimping ferrules - otherwise you break the wires with the terminal screw.
