Users with the User Administrator role can create users and manage all aspects of users with some restrictions (see below).
Only on users who are non-admins or in any of the following limited admin roles:
* Directory Readers
* Guest Inviter
* Helpdesk Administrator
* Message Center Reader
* Reports Reader
* User Administrator
Reference:
https://docs.microsoft.com/en-us/azure/active-directory/users-groups-roles/directory-assign-admin-roles#available-roles

Explanation:

Microsoft Purview auditing solutions provide an integrated solution to help organizations effectively respond to security events, forensic investigations, internal investigations, and compliance obligations. Thousands of user and admin operations performed in dozens of Microsoft 365 services and solutions are captured, recorded, and retained in your organization's unified audit log. Audit records for these events are searchable by security ops, IT admins, insider risk teams, and compliance and legal investigators in your organization.
This capability provides visibility into the activities performed across your Microsoft 365 organization.
Note: Permissions alert policies
Example: Elevation of Exchange admin privilege
Generates an alert when someone is assigned administrative permissions in your Exchange Online organization. For example, when a user is added to the Organization Management role group in Exchange Online.
Reference:
https://learn.microsoft.com/en-us/microsoft-365/compliance/audit-solutions-overview
https://learn.microsoft.com/en-us/microsoft-365/compliance/alert-policies

Reference:
https://docs.microsoft.com/en-us/compliance/regulatory/offering-iso-27001