Retention & delegation

Hi,

I have a question regarding retention policies.

When I want to delete a user, it offers me an option:

"give another user access to the "user account name" OneDrive files for 30 days after the user is deleted."

If I have the option enabled for the whole tenant & I don't choose (click) this option when deleting user, will retention option still go to my manager?

How ODB know where to send the link? Basically, from where he reads "manager field"?

Even if I enable this option for the whole tenant, will I need to choose this option every time when deleting the user?

Following this link, it says "https://docs.microsoft.com/en-us/onedrive/retention-and-deletion"

"By default, when a user is deleted, the user's manager is automatically given access to the user's OneDrive", what if the person doesn't have a manager, do we need to click on that option anyway?

Finally, if a person has a manager that will receive access to the files after the user is deleted, is there a chance that I add more than one person?

Kind regards,

Dino