By default (using business accounts), Marketing Cloud Account Engagement creates new records as leads in Salesforce. This means that when a prospect is assigned to a user in Marketing Cloud Account Engagement, and there is no matching lead or contact in Salesforce, Marketing Cloud Account Engagement will create a new lead record in Salesforce and sync with it. However, you can also configure Marketing Cloud Account Engagement to create new records as contacts or person accounts in Salesforce, depending on your preference. To do this, you need to enable the option in the Salesforce connector settings in Marketing Cloud Account Engagement, and make sure that the connector user has the appropriate permissions in Salesforce. For more details -> 151617

If business hours are enabled for an engagement studio program, any email steps will be executed only during the specified hours. If a prospect enters an email step outside of the business hours, the email will be queued until the next business hour. Therefore, if a prospect enters a Send Email step at 4:30pm on Friday, and the business hours are Monday-Friday from 10am-4pm, the email will be sent on Monday at 10am

The following activities would make a prospect active in Marketing Cloud Account Engagement:
Submitting a Marketing Cloud Account Engagement form, which indicates the prospect's interest and consent to receive communications from the company.
Clicking on a custom redirect, which tracks the prospect's engagement with external links or downloadable content.
Visiting a Marketing Cloud Account Engagement-tracked page, which captures the prospect's browsing behavior and page views on the company's website. Reference: [Marketing Cloud Account Engagement Prospect Activities]

To troubleshoot why a prospect did not receive an email from a drip program, an Administrator should check the following tabs in Marketing Cloud Account Engagement:
The Audits tab to see if the prospect was on the correct lists when the email was sent. This tab shows the list membership changes and email sends for the prospect.
The Overview tab to determine whether the prospect is unmailable. This tab shows the prospect's email status, which could be opt-out, hard bounce, or do not email.
The Lists tab to determine whether the prospect is on the recipient list or any suppression lists. This tab shows the lists that the prospect belongs to, including any lists that are used to exclude prospects from receiving emails. Reference: Marketing Cloud Account Engagement Audits Tab, Marketing Cloud Account Engagement Email Statuses, Marketing Cloud Account Engagement Lists

You can define a user's role in two ways: during the import process or directly from the user record. During the import process, you can assign a role to multiple users at once by using a CSV file. Directly from the user record, you can edit the role of a single user by selecting it from the dropdown menu. You cannot define a user's role from the list view or through an automation rule. Reference: Create and Edit Users, Import Users