Does tapping the Yellow bird sooner have a greater impact on the structure?
It doesn't matter, as far as I know. There's two things to keep in mind with yellow birds:
- They are only effective against certain materials. They will rip through wood but seem to be particularly weak against ice.
- When you choose to click on the bird after launching it determines what kind of trajectory the bird will have; apart from going backwards, you can make a yellow bird strike a target at pretty much any angle.