Disable ADS data for a certain software service definitely save the resources of ADS machine, but would it save the resources of CAS machine as well?
My use case here is that the memory usage is quite high for CAS server, so I am thinking of disable ADS data collection for a software service that is related with the Proxy of my client's organisation, while keeping intact the ADS data collection for all other software service (which are related to their applications)
As you mentioned in your question ADS data is calculated and stored in the ADS database which is not going to make much of a difference to your CAS server. There is other investigative steps and actions that I would take to see if you can lower the memory utilization of your CAS server.
You can go to your: "https://yourserver/RtmGenCfg" and look to see how many client users you are tracking. You can check out your User IP address ranges and maybe you can adjust this configuration. (If Needed)
Additionally, a good approach is to determine what SoftwareServices are creating the most sessions which might be making your CAS work harder then it needs to be. In order to check this go to the administrative Console and run some SQL queries. Please see the screenshot below for the query I use to identify this information. You can access the SQL Console directly by going to this link: "https://yourserver/DiagConsole#/sql"