In this image, the top fonts (bad to do, extension) and the hero area (The worst to do...) are size 24px. However don't hard code it by pixels - use that as a reference, then make it so it'll look good on responsive as well.
The icons should be approximately the same height or slightly bigger than the text in the header.
https://monosnap.com/file/UXBya9w2yZqhslVHZObYBW7xEcilO1
In this image, the top fonts (bad to do, extension) and the hero area (The worst to do...) are size 24px. However don't hard code it by pixels - use that as a reference, then make it so it'll look good on responsive as well.
The icons should be approximately the same height or slightly bigger than the text in the header.
In the image, the button text is 18px.
Here are some notes on the image above: https://monosnap.com/file/D4QDu2JVAQVr1Meu9hZkkLWAAoomWL