"Kentico User", by default, Kentico will use the email queue AND batch process emails. So if you're sending out 1000 emails to subscribers, it will:
- When you click send in the newsletter, it will process the newsletter emails,
- Then it will place all the processed emails in the email queue,
- Lastly, it will batch process them based on your settings
To answer your question regarding the "From" email, typically when there are more specific properties in a module, they will override what is in the Settings. So in this case (I've not tested it) hypothetically, the From email address in the campaign email will be used over the settings value.