Navigation breadcrumbs will appear when clicking on the . The drop down will show the root level plus the level onwards below it. Clicking on a level will redirect you to that folder.
The root level is Documents, and will show a icon when you are in this folder rather than the icon.
Users will need view permissions in documents. Depending on the settings of a user's project permissions, they may be able to view all document entities, or just a subset of them. Folders and files marked as public are viewable to any users with view access to the Documents section, so it will not have shared members. Entities specifically shared to a member will be viewable to them.