OPCDA.NET-UA bases on the OPC Foundation UA SDK with the WCF based communication stack.

The communication options are configured on the server side. The client can only choose one of the available endpoints.
OPCDA.NET-UA selects among the available endpoints the one that matches the application specified URL scheme (http, https or opc.tcp) and the highest available security level. If such an endpoint is not available then an available one is selected.

UA server discovery returns the available endpoint URLs with the proper syntax. If server discovery is not supported (e.g. because the server is remote) then the client application needs to get the proper URLs from the server documentation or another toll such as a local test client.