Will the slicer blade stop immediately after an emergency stop?

No—once the emergency stop cuts power, the blade keeps turning for a while because of motor and drive inertia. Whether it halts on command depends on whether a brake is fitted, how it works, and the inertia of the blade or blade assembly. Get the supplier to state the stop logic in writing, plus the measured time from pressing the button to the blade coming fully to rest, and specify whether that figure was taken unloaded or with product. Verify it yourself with a tachometer or marker method behind full guarding, and note reset and restart conditions along with the brake's adjustment and replacement interval. For a slicer, edge condition and blade locking deserve their own check; an over-long stopping time fails acceptance.