Hi,
Thank you for asking this question on the Microsoft Q&A Platform.
I guess you are on the right path with regards to setting up the auditing on the DC via the GPO, also this link will provide details tracking and notification of each user activity. So can be used and yes it will be bit of extracting the logs and filtering out as per the requirement. monitoring-active-directory-for-signs-of-compromise
Recommended and I have used SCOM product to monitor and alerts as per requirements details.aspx
Also Solarwinds is a good tool but it is third party so please review docs and decide which one is preferred by your team.
user-activity-monitoring
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