I can't answer your question, but after a lot of experimenting and reading I ended up with styled-components as my preferred solution if I were to go the SPA wa

I can't answer your question, but after a lot of experimenting and reading I ended up with styled-components as my preferred solution if I were to go the SPA way. It allows you to write your CSS inside the backtick js strings (template literals?) and then inserts/removes the relevant CSS as components are loaded/unloaded. Personally I've gone in an entirely different direction (server-side everything, and simply diffing the HTML on the client when necessary), but if I were to build a proper front-end app, I'd probably go for styled-components. The main downside is that the stuff needed to parse the css-in-js-string is yet another thing that increases payload size, but for an app it's not too bad.