Hi,
Although the ArcGIS Runtime SDK for WPF uses a "local server" to host local content for offline use, there is not one central local server on the client machine which may be hosting any number of services. When you deploy your application, you also deploy an ArcGISRuntime deployment folder. That folder contains and number of ArcGIS Runtime components, including what will become an instance of the RuntimeLocalServer. That instance is only used by your application, hence the port numbering and unique prefix (both of which you can control via the LocalServerUtility tool). There may be multiple WPF applications on the machine, but each will be using it's own RuntimeLocalServer instance. Therefore, the only services you'll be accessing are the ones your application has created.
Each local server is seeded from a package (Map, Locator, Geoprocessing) and therefore when working with offline content your application really works with packages and the local Layer types that expose them. Although it is important to understand the architecture, the fact there's a local server is really just an implementation detail.
Cheers
Mike