with 2-3 K mails pr week you should go with gsuit and gmass.
“what the real difference is between say mailwizz /Mautic and sendgrid , sendinblue, sparkpost? ”
mailwizz /Mautic is a form of mail client, like outlook. You do your daily tasks, organize, design emails, follow up things , contact management (emails) etc.
Sendgrid , sendinblue, sparkpost? are extern smtp (relay) provider. You pay for their service. When you want to send mails out from mautic you need an smtp server like sendgrid , sendinblue, sparkpost or your own mailserver.