PostCSS vs PurifyCSS vs Sass

Originally, I was going to start using @{Sass}|tool:1171| with Parcel, but then I learned about @{Stylus}|tool:1172|, which looked interesting because it can get the property values of something directly instead of through variables, and @{PostCSS}|tool:3339|, which looked interesting because you can customize your Pre/Post-processing. Which tool would you recommend?

JSS is makes a lot of sense when styling React components and styled-components is a really nice implementation of JSS. I still get to write pure CSS, but in a more componentized way. With CSS post-processors like SASS and LESS, you spend a lot of time deciding where your .scss or .less files belong, which classes should be shared, and generally fighting the component nature of React. With styled-components, you get the best of CSS and React. In this project, I have ZERO CSS files or global CSS classes and I leverage mixins quite a bit.