Excessive nesting in SASS or SCSS can lead to bloated and inefficient CSS files, which are larger in size. This negatively impacts loading times and page performance. It is advisable to avoid deep nesting to keep the stylesheet lean and maintainable.

A font's loading performance can be improved by "preloading." Preloading involves using the link element in the HTML to fetch and cache font files in advance, reducing the time it takes to load and render text with custom fonts.