In the campaign flow, do tasks after a scheduled task happen immediately or do they happen sequentially after the scheduled task has been completed?
When you configure multiple tasks within a campaign, ALL tasks are executed immediately -- even if there is a scheduled delay for one or more tasks that send emails to the contact.
A campaign does not stop its flow when there is a timer scheduled for an Email to Contact task. All of the actions in a particular chain happen immediately. For Email to Contact tasks, the email is immediately scheduled to be sent at either an absolute date and time or is scheduled to a time relative to when the user pressed Submit on the web form.
Note: If your tasks include multiple actions associated with web forms, either serving a web page or redirecting to a different URL, only the first action is executed to ensure a positive user experience. For more information on this, refer to Answer ID 2177: Redirect to URL Task does not Work.
Note: "after previous action" does mean it will be after the campaign was submitted