Fonts are one of the most important resources. Custom fonts, and iconsets usually are important for an impressive design, and many pagebuilders are using them. However it can happen that your site is loading 2-300kb fonts which can increase LCP, FCP and CLS as well.
If you enable Smart Font Delivery feature, Swift Performance will create an optimized version for fonts what your site is using in the “above the fold” content, and replace the original font files to the optimized one in the Critical CSS
You need to enable Advanced View to see this feature, also Merge Styles and Critical CSS need to be enabled. It is also recommended to preload fonts.