Spool is like axel, one way is only turning if you put force in one direction on other it`s off. Differential is same old power differing between two tyres thus inner wheel when turning turns slower than outer. I one tried drifting really liked diff/rear and one-way/front. Usually only diff is on rear axel and spool, one-way or solid one-way(like spool and one way in one) is used in front.
there are a bunch of threads on how each one works and what each one does. As far as drifting its going to depend on how you drive and what feels good to you. Preferably i like to use either a ball diff really tight or a rear spool and a front one way setup because you can use your brakes as an e-brake to get the rear around but it will lock up under accel and pull you out of the drift
Hot Bodies Cyclone - - TeamTekin - - Spektrum - - Team Orion - - Futaba