In the end my choice to stay in Seomyeon worked out pretty well. The Airbnb wasn't as nice as it claimed to be but it was fine for a couple of days. Getting around by subway was easy and I walked a good bit too.
I did a night time tour booked through Airbnb which was quite good. The guide picked us up at one of the subway exits and drove us to several good viewpoints including a nice mountain view over the whole city.
Definitely didn't have time to see everything but it was a nice intro to the place.