I keep both sliders all the way up. This allows anyone links in OneDrive, but by default will leave group connect / Team connected sites as "Specific people" only options. As Juan said you can run powershell and restrict all your SharePoint sites from Sharing, but honestly, if you restrict documents, all you are doing is making it harder for them to Share, if they wan't do, nothing keeps them from downloading the file and tossing it as an attachment in e-mail.
Do you restrict sending attachments in e-mail? If your answer is no, it's better that they Share the document than to make a copy and send it on. At least with Sharing, you have audit logs to determine what files were accessed by whom.
I dunno, just a few thoughts behind my reasoning to not restrict it down. To each their own on the topic, but best way I've had is allow it all, and set the default setting to specific people and not have the default anyone links, this makes people consciously think about their sharing options.
