The build you put in the Goblin also is a defining factor on how much the air can be restricted. Large coils will restrict the draw and create a warmer vape and Thinner/Smaller diameter coils will alow the full amount of air to flow through. Wide open is alot like the Derringer with a hole cutoff each side. With the GM closed almost off it has around he same airflow as a Vivi Nova Tank....
Its a great tank and if you have a drill and tap set just drill and tap the top metal cap to use the same bottom fill screw or similar and then you have top fill....
My Goblin Mini:
As you can see not much air can get through so it gets warmer then most builds Ive used in it and having it wide open still feels like its closed down a smidge less then halfway open...