How to handle WP Customizer and Theme Styling



I’ve been looking into leveraging SASS to handle styling my themes and the thought of storing various styles in variable to be used across the site is really helpful! Eg. I am able to store the Raleway font in a variable and re-use it across my stylesheets.

What I am confused about however is how I use this in conjunction with theme options (specifically WP Customizer)… Eg if a user of my theme wants to change the font-family from Raleway to Lato, does this mean the variable needs to be changed in the sass file then re-compiled? At what level should this change be made?

At the moment my theme options (in WP Customizer) are being injected into the page head… surely this is not best practice?