Can I have guests submit a front end form and it be saved as a draft for approval by an editor or must they be a registered and logged in?
Yes, visitors can submit a front end form. I think there are some limits on some fields, like images and files.
To create/save a new post and alter the status of the post you’ll need to add a pre_save_post filter. See the documentation here: http://www.advancedcustomfields.com/resources/acf-pre_save_post/