That is not Kim soo Hyun's account, that is one of his fan page with similar name, soo Hyun's official acc with profile pic of black background, he worn black shirt
Bubble is paying application (SM and JYP, other artists) same as Weverse (HYBE and other artists)... They can interact directly to their fans (that is why you have to pay for it)
Right I didn't know about the bubble 😁, but I will be very happy if jiwon and soo Hyun endup together in real life as well 😍❤️, such adorable they are... Watched Qot only for them, literally waited for a year from the announcement of Qot script reading.