Amazon FSx for Windows: Tracking User Quotas for Files owned by AD Groups

With FSx for Windows, quotas are done either at the group or user level, not both. (unless something has changed in the last 6 months)

Given your line of questions, I think that the statement makes some of your questions moot.

To answer your questions with latest information :

1. User Quota can be assigned to AD users & Groups both, separately.
   Set-FSxUserQuotas -Domain <Domain> -Name <User\Group> -Limit <Limit_Size> -WarningLimit <Warning_Limit_Size>

   https://docs.aws.amazon.com/fsx/latest/WindowsGuide/managing-user-quotas.html

2. Files are owned by user who creates them, hence if the user is a member of AD group for which quota is applied then the quota will include the files created by the owner.

3. Not with storage quotas but certainly with recent launch of FSRM Quotas, specific shares can be set as Quota Target. https://docs.aws.amazon.com/fsx/latest/WindowsGuide/fsrm-quota-management.html#fsrm-quota-management-commands