Hi,
The Server 2016 KMS key could activate Windows 7 Clients once you reach the 25 client request minimum. Server KMS keys activate all server and client
OS at or below its level so a Server 2016 key will activate Server 2016, 2012/R2 and 2008R2 as well as Windows 10, 8/8.1 and 7. We could find the information in the picture below.

Ifwe added Windows Server 2016 KMS keys to the KMS server, you have nothing special to do.
In order to activate clients, the KMS uses a KMS host key. This key can be obtained from the Microsoft VLSC (Volume Licensing Service Center) website.
Because KMS host key of newer Windows version can be used to activate older Windows versions, you should only obtain and install the latest KMS host key available in VLSC.
You could understand Volume Activation Services for KMS by checking the information in the link below.
https://secureinfra.blog/2019/01/13/understanding-volume-activation-services-part-1-kms-and-mak/
Regards,
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