I think the three levels all have merit. If you don't end up repeating yourself too much, just add the utility classes directly. If you find yourself repeating

I think the three levels all have merit. If you don't end up repeating yourself too much, just add the utility classes directly. If you find yourself repeating a bunch of classes together, maybe you can make a semantic class with @apply. If you're repeating a bunch of HTML (and Javascript) along with the CSS, make a component.