Access controls are only available for users with an account currently. Even if you set 'Anyone with the link' to write, they will need to be logged in to write to the directory.

Users can always delete files they uploaded themselves, even if they don't have delete permissions. You can see who the owner of a file is in the Details window.

Link permissions
Anyone with the link can...
User permissions

Enter a username here to give them access to this directory. The user will not receive an e-mail invite. Giving write access to a user without giving read access as well does not actually allow them to write anything.

Password permissions

Allow users to enter a password to give them access to this directory.

This feature is not implemented currently!