Yes! In your settings under Website Styles you can input any Google Font (https://fonts.google.com/).
It is case sensitive, but that'll allow you a ton of flexibility to customize fonts for headers, text, buttons, etc.
As for email, you can visit Email Template under Settings and choose different fonts for each individual type of component in email (header 1, header 2, paragraph text, buttons, lists, etc.).
The email font options are a bit more limiting due to restrictions a lot of mail clients have on fonts, but we provide a handful to choose from and can look to add more in the future.