Are there any added benefits for using Apollo client with Apollo Server over using another client lib with Apollo server ?
Welcome to the community, @Benjamin!
The Apollo client libraries come with a very rich feature set. The most important features are code gen, caching (huge), and native Kotlin/Swift constructs for Android and iOS libraries. That being said, it depends on your use case and the requirements you have. You can even do the HTTP POST requests including the query/mutation in the body yourself to get back a response from the server.
Hope this helps!
It makes some of the full-stack features of the Apollo Platform easier to use and configure, like Automatic Persisted Queries and Client Reporting in Apollo Studio.