Just to confirm that I understood this correctly; with "Enable account activation letter"  Unchecked and "Enable profile activation letter" Checked, the user will only receive two emails:

1. 'Confirm your Email, please [Action Required]'

User clicks/confirms Email, and then receives second email:

2. 'Profile activated.' (This should instead say 'Account activated', since no Profile has been created yet).

In general, this Account/Profile thing is confusing. Account is Account and Profile is Profile. The user creates and confirms one account, and then creates profiles.