How often are YOU running into the "super lucky" opponents?

if i understand the sliders and console ai correctly, the only way in order for a player to prioritise spells over gem matches is to slide the gem sliders to the left?

and also am i correct: do the sliders multiply priority over gem matches only (and gem creation)? do the sliders not help determining the choice which troop will cast (if they are all full) for example?