I think gestures and incantations (along with how the spells actually manifest) are a big part of a wizards style and therefore extremely important. Imagine if Harry would just stand around and think attacks onto his opponents. That would be extremely boring. Imagine describing a combat between 2 wizards like that.
However, that does not mean that every wizard needs to be all about flinging around the damage. A more subtle wizard would have more subtle gestures and incantations. Maybe just moving his fingers a bit, drawing a small symbol into the air in front of him.
I guess it all boils down to "magic is what you believe it is". And for most wizards it's probably along the lines of more power = louder and bigger gestures.
But you don't really have to burst through barriers. If there are bars in front of a window, you could simply maneuver a "metal to rubber" spell on them and climb through the now deformable bars. That would certainly be in style with a more sneaky wizard, and it is a cool way to get around things. And that doesn't mean a wizard like that would have to be boring.
Harry doing the summoning ritual entirely in his head. Along with Small Favor, it is great for comparing the difference between Harry's and Molly's styles of magic.
To get people to do things like that, I would use a good old compel. Is your wizard the flashy fiery smash first, ask later kind of guy? Compel him to behave that way. If he does not want to smash his way through, he can pay a fate point. And in that case, I would not add to the difficulty, he paid a fate point after all.
And the other way around, too. If your player makes a subtle wizard, remind him of that every once in a while, especially in combat situations. That does not mean he would not be able to fight, but it would mean, he would have to find a more subtle way to do so, closer to his style.