How can I create a page with resources that is not private, but also cannot be accessed by any visitor?

If you do not want to make the page private, when you create a public page it will only be accessible to visitors if you assign it to a menu. If you do not link it to a menu tab, the only way people would have access to is when you actually give them the direct URL. The page will therefore be "hidden" (but not technically private in its settings) and you can just give the specific URL to your clients.