Sharing (really) secure
There is still no difference between email and link sharing in OneDrive. Whether by mail or by link, the person to whom I send the email or the link can, if it wishes, transfer the link or the email to a person with whom I do not want to share my documents oneDrive . The solution of password does not change anything since if the person transfers the mail or the link, it will give the password also.
There should be, when I share by email, an identity check when connecting to my oneDrive documents. As for the oneDrive business I use as part of my job. With the company oneDrive, I share with a person and if this person transfers my mail and access will not be distributed.