Usually the dist folder is for shipping a UMD that a user can use if they aren’t using package management. The lib folder is what package.json main points to, and users that install your package using npm will consume that directly. The only use of the lib as opposed to src is to transform your source using babel and webpack to be more generally compatible, since most build processes don’t run babel transforms on packages in node_modules.
As far as handling the style imports, it’s probably a good idea to not import scss or css files in your source js that you export. This is because node can’t import styles like that by default. If you have an example that demos your component, it makes sense to import the styles there. The common pattern is to publish minified and unminified css in the dist folder, and in your documentation tell the consumer to explicitly import the css file using whatever technique they prefer. I took this approach with redux bug reporter if you need an example. Hope that helps!