Font types / sizes for specific objects are not configurable. The most that can be done for some objects is to specify size in the form of (Small, Medium, Large). This is due to the responsive nature of the interface to automatically configure itself for the optimal viewing experiencing depending on the device used.
However, there is a theme engine that can be used to configure various style properties using a text file. It is experimental at the moment. If you are interested please check out the solution to this post: