Thanks for writing in!
The Typography settings for the body and content can be found in X > Theme Options > Typography. Please also check whether the font manager is enabled or not. For more details about the font manager, please check this out: https://theme.co/apex/forum/t/font-manager/101/1,
The logo font can be changed in X > Theme Options > Header > Logo - Text.
Please be advised that Cornerstone is a page builder. When you use Cornerstone to create your page or post contents, you will have more options to control the elements and its styles to display in the content.
To get started with Cornerstone, please check this out: https://theme.co/apex/forum/t/cornerstone-content-builder-introduction/118/1
Hope this helps.