Hi lheath,
Currently, in Office 365, SharePoint Online does not have a feature or provide any tools to complete the backup directly. About the contents and settings backup, I would like to provide the following instructions for reference:
1. To back up the documents, you can simply keep a copy locally to achieve the backup goal.
2. To save the settings of a site, you can save the site as a template. You can also make the template include its contents. However, the size of the template is restricted. If you have lots of documents in this site, including the contents is not recommended.
To save a site as a template, you can refer to the following article:
Save a SharePoint site as a template
Thanks,
Kevin Cui