You absolutely can, and I almost always do, styles things with native css (well, I use sass compiled to css) to style your react application (or widget!). To m

You absolutely can, and I almost always do, styles things with native css (well, I use sass compiled to css) to style your react application (or widget!). To my knowledge, React itself has no opinion on styling. It's more the ecosystem around React that's gone css-in-js. But, yes, if you want to do your styling natively that's really not a problem.