Anything I can say about the similarity between the two would be a spoiler for story.
Basically they both have exact same vibes
The story, the plot, the characters are different but the underlying setup is too similar.
Anyone who watched both will understand what I am trying to say. Especially in the last 3-4 episodes.

Repeated timelines while trying to achieve better ending.
Queen In Hyun's Man is a romance heavy drama, with much less plot holes than lovely runner, and the acting is to the point.
Lovely Runner on the other hand while it is a little weak on the acting and pacing part, it's full of fluff from start to finish.
Both are rom com. Recommend both of them.