I'm looking for an extension to be able to add/edit custom CSS in the admin panel, instead of editing a css file in the theme's directory. It would need to be compatible with any theme. I'm trying to avoid having to edit files in the file system as much as possible. I found this extension and it looks like it will do the trick:
Would that be the best option or are there better solutions?
In Wordpress, this is usually handled by the theme installed. Many themes have a "custom css" field where you can add in custom css to override the default theme styling. It allows you to avoid having to make these CSS edits in the file system.
I dont think it's a good idea, if you need this maybe magento is not the right platform for you.
Css files are compiled from less and then deployed with other static content, you can't simply edit css in a backend panel lilke in wordpress.
Customising CSS in the admin panel is not a good idea from the performance point of view. Magento designs are built on LESS css and they are compiled after you deploy the website.
Whenever you write css in the admin panel, it is applied as inline css to the frontend and it has a minor negative effect on the SEO and SERP rankings too. Given that magento uses Full page caching and varnish, it is never a good idea to have css as inline css.
I'd recommend writing your own css in less files and then put them live.