the Theme icons, such as the Menu Toggle, Back to Top, Category icons etc. are currently loaded using a font.woff file – selecting the SVG option in 2.3 will replace the font with inline SVGs.
This means one less request for the font file and removes any font warnings that google may raise in regards to using a fallback font.
the SVG option will be available in GeneratePress 2.3 (currently in Beta) under the Customizer > General options.
Samuel – FA is probably the easiest way of adding FA icons but as you know the library is huge and really overkill when you only need a couple of icons. So yes the other method would be lighter.