Those ventral fins on the lower rear fuselage of the B737 AEW aircraft (or indeed on any aircraft) will improve directional stability but will not help directional control - the latter arises from the fin/rudder, and they won't be helping that unless there's some really weird cross-flow on the rear fuselage.
Now in single engine the yawing tendency induced by the engine is counteracted by the directional stability of the plane, which tends to reduce the sideslip the yaw can generate (which the fins do help with), and by the directional control (rudder) which is then used to further reduce the sideslip angle. So the fins may help with the Vmc case, but not with 'control'.
On "strakes" vs "fins":
I very much doubt they are actually strakes, but probably are (auxiliary) fins - the different between the two being that a strake is a flow control device, which doesn't necessarily generate any large direct forces but instead does something to the air flow which helps the characteristics indirectly, whereas a fin is usually a direct acting surface, generating a load of some significance on itself.