Viscous LSD doen't usually have 'way' like mechanical multiplate LSD. You can't really consider it as '2 way' as the fluids is what make the wheels spin at the same speed, unlike mechanical LSDs where locking 'way' is determine by the way the cam groove is designed. I would say viscous is '1 way' coz it doesn't really lock (half for acceleration, half for deceleration, if you catch my joke...), and often the response is slower (or very slow) compared to mechanical LSDs.
As for drifting, mechanical multiplate LSD are recommended, and preferably AT LEAST a 1.5-way, although a 2-way will do the best. You wouldn't want a 1-way LSD for drifting, as it doesn't have any locking rate during deceleration, which will make it quite difficult if you want to do some weight transfer trick to kick the tail out, or switching side trying to maximize your drift angle.