Her early performances rightfully led to some criticisms as she could look a bit gormless and stiff, but I have to say, I'm massively impressed with her acting in recent works.
In Rookie Historian and Run On she is really good and, in the latter, has no issue keeping up with Im Si-wan who is a very good actor in his own right. Shame she had a bit of a break after Run On but curious to see what kind of projects she tackles in the future as she always had the actress visuals and can now back it up with great performances.
I think IU would fall into this umbrella for me as well but still slightly undecided.