When configuring an SFTP user in Marketing Cloud, the following considerations should be taken into account:
B). Minimum password length is 12 characters: Ensuring password security, Marketing Cloud requires SFTP passwords to have a minimum length of 12 characters.
D). Once created, the user will need to be activated in order to use the SFTP: After the SFTP user account is created, it must be activated by the admin before it can be used for file transfers.
Reference: Salesforce Help - Manage SFTP Users