what is the good way to manage styling (css) in angular?

Your question will become important if you are working on a team of different people, and every different person uses his own class names, and conventions in different components. You will want to pull your hair out. It is a good idea to create common classes in styles.css or another stylesheet so that you have a sort of library of css classes to choose from rather than giving each developer complete freedom. This will become especially relevant if you use bootstrap which I personally find difficult and timeconsuming to work with.

you can do both depending on your requirement