My experience from model tugs;
Twin Kort;
Right hand prop, 'right handed turn' makes the tug manoeuvrable
Right hand prop, 'left handed turn' gives greater thrust with slight drop in manoeuverabvility.
Single Kort; no difference right or left handed.
Without Kort;
single prop, either right or left will prop walk in that direction at slow speed
Twin prop, right hand prop, 'right handed turn' much the same as with Kort but noticeably accentuated with the observation of wasted energy/pull if under high throttle, as this produces a rooster tail which matures to excessive cavitation.
just my observation
Regards
Pirate