Integration with Mailjet: which contact database is used ?

I want Newsletter to compose my newsletters with Newsletter
I don’t want Newsletter to manage my contact lists and database

I want Mailjet to deliver messages AND manage my contacts lists and database

Reading your documentation, it seems that Integration ” Newsletter – Mailjet” means
compose the newsletters with Newsletter
use contact lists from Newsletter
deliver message with Mailjet

Is that correct ?

Plus :
I don’t use Brevo but in their documentation about integration with Newsletter or another plugin they specify that they use their Transactional Platform (and not their eMail Marketing platform): that means that they take the contact one by one from the WP Plugin and send it as a transactional email. ( which must be far less effective than a email marketing campaign process)