While bugs, taken collectively, are very effective, some are more effective than others. Previously I wrote about Tom McNally's introduction to bass bugs with longer hooks set at an angle to the body. The bug's motion doesn't draw enough strikes. The first thing to consider when buying or building a bug is hook clearance. Even a relatively soft material like deer hair will impede hook ups.
Motion is critical.
Even bugs which are allowed to sit still on the water move. You won't see the motion from forty feet away, but the fish will. Remember that bass and bream won't eat something that looks dead. In open waters, where motion can be imparted by the retrieve, body shape becomes more important. Cupped faces, flat faces, slanted faces, lips, collars, or a combination of these shapes, determine how the bug moves.