Since you added more to your post, I wanted to quote it again and reply to the rest.
I think Yadech could be considered a koo kwan for their immense popularity; however, in my personal opinion, I don't think they have exceptional acting skills either. They're more of a couple that is loved mainly because of their looks and interactions, as MOST pairs nowadays are. Whereas, in the past, koo kwan couples like Ken and Anne had the WHOLE package: good looks, great chemistry, and amazing acting. No pair in this generation, I would say, is a full package koo kwan, or even a koo kwan at all. Haha.
But Kim can make it on her own. She doesn't need an actor to make her rise to fame. I have always believed that she will be a top actress, if not THE top actress, in the future.