Encrypt versus Strong Encryption

If I understand it correctly, the Encrypt and Strong Encryption both are encrypted by a key that the users enters from the frontend.

First, if you set the Encrypt mode, can some users continue to opt not to use encryption, while others can use encryption at their individual discretion?

Second, why wouldn't you use strong encryption versus the encrypt mode? What are the pros and cons of these two options?

Thanks

The FAQ expains the different modes. Strong encryption uses 3DES while encryption uses a simple XOR'ed key.

When a user does not enter a code the email is not encrypted.