I have been struggling with these question for way too long. After writing tons of unmaintainable and side-effect heavy CSS I think I finally found some solid ground rules to answer these questions.

The padding-inline CSS shorthand property defines the logical inline start and end padding of an element, which maps to physical padding properties depending on the element's writing mode, ...

I believe CSS borders and padding would be more intuitive if borders could collapse into padding. A css-like box model which depicts margin, border, padding, and content. In the model, border is shown ...