All your strings will indeed be 2 byte characters in the application. They will be written to the database in the character set as defined in the database itself. This does not depend on any client setting. Your application will work exactly as before, will read and write the same characters, even though they are now 2 bytes instead of 1 byte.

The ConvertUTF option will indeed be cuUTF8ToUTF16. This is the only option that makes sense in a Delphi XE application. Other options are only relevant for older Delphi versions with single-byte string data type.