Hi Sumbul,
The Dual device you specify would be more likely to connect to the device rather than connect directly to Survey123; with Android & iOS devices that is the normal way to connect to a GPS (especially when you are not doing a high-accuracy collection, which the Dual device looks to be unable to support). Once the GPS connects to the device, it overrides the built-in GPS; Survey123 will see the information from the device by default then.
As Lance mentioned, Survey123 can directly connect to an external GPS receiver. Note that for a direct connection to be supported in iOS, the Survey123 needs to work with the device manufacturer to authorize the application to use the device; this has not been done for a Dual device at this time.