We can write CSS as the following types:
I would like to know pros and cons of each.
To everyone in the here and now, reading after 2015, with projects like Polymer, Browserify, Webpack, Babel, and many other important participants that I'm probably missing, we have been ushered into a new era of writing HTML applications, with regards to how we modularize large applications, distribute changes and compose related presentation, markup and behavior into self-contained units. Let's not even get started with service workers.
So before anyone forms an opinion on what is and isn't feasible, I would recommend that they investigate the current web ecosystem in their time to see if some issues related to maintainability have been gracefully solved.