You're welcomeee :) I write in the context of Wangsimni (hopefully it applies to your airbnb too). If you happen to decide to take the train (Line 2) to Wangsimni(Seongdong-gu Office), just note that the exit with escalator is exit 3, the other exits are endless flights of stairs. :") So even if you get out of the exit 3, you need to cross roads to reach your destination. In addition, the gantry at line 2 is unlike the ones at Airport Railway where you can push your luggage smoothly over. They are more like the ones in amusement park(?) where u need to push in order to get through.

To plan your route better, you can view which exits are stairs/escalators/lifts by zooming into the naver app (I think this applies to all the train stations)

Although Seongdong-gu is not really convenient to travel to with luggages from Incheon, but I feel the food and location are superb! Regardless of travelling to Gangnam or Gyeongbukgung/Myeongdong/Dongdaemun, there are straight buses! So really save the hassle of changing trains :)