Yes, in C#, we need to use the Managed DLL (Microsoft.FlightSimulator.SimConnect.dll in the SDK) to access the methods, properties etc of SimConnect. We can’t natively use the SimConnect.dll directly without a lot of hassle and additional coding.
Regarding your comment about using the Plug-In route, that sounds like a better option, as you can then completely remove it from memory before re-creating it, ensuring there’s no legacy code left to retain/cache the config values.