I would suggest the use of convention like SuitCss for your custom component classes so you can lint them thoroughly to ensure low specificity.
I would recommend to use a prefix on your custom classes, to "namespace" them. "btn" is far too generic. This can even be linted by eg. postcss-bem-linter.
I would recommend to use a prefix on your custom classes, to "namespace" them. "btn" is far too generic. This can even be linted by eg. postcss-bem-linter.