Why do you need to add spacer divs? As long as the child components accept classes as props then the styling comes from the parent but is still applied on the children.
You can also apply margin via element and nth-child selectors, just as a note... Also - custom/shadow dom elements should allow classes - I think it doesn't work in angular yet - but should arrive in the next version(?). Also you could just use ::before ::after pseudo selectors instead of divs...