I think this can be achieved. When you create a copy of your production system, you can select which data you want to copy- you can select no for users and application data.
You can use SAP TEST DATA Migration Server TDMS, to transfer limited data to test instance however it involves extra cost and not recommended until it is really required. Refer this link to know more on TDMS:
You can keep both the instance- Prod and Test synchronized by using Transport Management System TMS where you can schedule transport to load data to training instance. With use of Change and Transport System (CTS), you can manage transport and changes between the SAP systems in your system landscape. As well as ABAP objects, you can also transport non-ABAP objects and non-SAP applications in your system landscape.
To know more about SAP TMS, you can check this link: