If you haven't already, download the React DevTools, and when the React app is properly deployed, the Chrome DevTools shows the React Components and Profiler tabs alongside the usual DevTools tabs. From the Optimizing Performance React docs, we can prove that this is a live React app by clicking on the extension's logo to see this:
I went to the browser and verified the build sizes were indeed very small:
My build was 3 requests with 158 B transferred.
70% of sites are larger than 1MB, which take 5 seconds to load, per Google Lighthouse Audit.
The build is working and deployed on: https://hashbangash.github.io/dojo/.
If you want to add a css file, check out my current build to see how I added it. React has lots of different ways to do styling, such as Sass, inline styles, styled-components, etc.