Incantation and your characters personal, magical keywords play a big role on your spells strength. Though rank does determine the damage, destruction, properties and range and such of a spell, the incantation is what gives the spell its full potential. To fully amplify your spells power, you must role-play your character fully saying the spells incantation.

Incantations may slow down your spell, but spells with full incantations are much more deadly then silent incantation or one-word incantations. This is because; silent incantations lose power to increase the speed of initiating the spell they want to use. That usually involves mastering the spell you plan to use, however some people have fighting styles without incantations, so they lose the velocity and power of the spells and instead unleash fast, furious spells.

Not only that, but magical keywords are a must to make your spell a powerhouse. Every magician has magical keywords, even Evangeline, a master magician had to use keywords to make her ice spells tower up to that of a tower. No matter the rank of the spell, you need to chant your magical keywords to build up the power of your spells. I hope this clears some things.