It's good to hear from you today, Aoun Ali.
Allow me to share some insights regarding purchasing QuickBooks Desktop Enterprise 20.0.
For your first question, yes, you can add five more users in QuickBooks Desktop Enterprise. This version of QuickBooks can scale up to 30 users. For your second question, the Admin user is already included for the five licenses.
The multi-user mode in QuickBooks allows multiple users to install and use the same company file at the same time over a server network. The following resources will give you more details about adding and restricting user permissions in QuickBooks Desktop Enterprise:
QuickBooks Desktop Users and Restrictions
Create users and roles
Please let me know if you need additional assistance. I'd be glad to help. Have a good one.