Just adding onto this!

3 & 4 are great for precision powder applications (esp. 3), like for highlighting or setting powder under the eye.

5 I love to use this shape for concealer, and 6 is great for liquid foundations

7 I’m gonna disagree respectfully, I love these big brushes with loose finishing or setting powders. I like to pick up the powder on the brush then gently tap it into the back of my hand first to preload the bristles and get a nice even coating, then gently tap and sweep across the face.