1. To change the general font setting you can setup it on the Customize > JNews: Font Option > Global Font. Also, we have been including Yellow Pencil plugin into JNews theme package that you can use for adding custom style (frontend style editor). With this plugin, you can easily add custom style to each element for global or for certain page/post only.
2. We’ve provide an option to control the overlay color for the hero module element. But it’s a new feature and it will available on next version of JNews. Can you tell me which hero type that you want to change the overlay color? I will give your custom CSS code for a temporary solution.