You can do either (or both) but the advantage of the contrib is that it establishes an open connection to the Blynk server and will trigger a Write Event node whenever a widget in the app changes state. This means that if you have a button widget attached to V1 then the Write Event node attached to V1 will go from 0 to 1 when the app button is turned from off to on.
To achieve the same functionality with a GET API you would need to keep polling each virtual pin to look for status changes.
Have you read this topic…
Pete.