Wanting to move static/single templates in to a directory
pages and thus, the path to my 404 template is now
pages/404.html. I don't necessarily need dynamic content as asked here. Is there a config setting I can use to point the default 404 URI behavior to that template?
Yes, use errorTemplatePrefix.
'errorTemplatePrefix' => "pages/",
Here's more than you ever wanted to know on 404 and error templates in Craft CMS: Handling Errors Gracefully in Craft CMS