Both are Historical Cross-Dressing Romances. In both the fl is surrounded by four handsome male characters. The male characters personalities are similar in both dramas, for example they both have that cold swordsman type etc. Both dramas are also really lighthearted in my opinion, they give off similar vibes.

The girl MCs after experiencing hardships during their relationships in life had a total personality change. Through a series of events, they became seventeen again solely in mind. If you don't believe this was properly explained, you can read the summary. Love @ seventeen is a series whereas suddenly seventeen is a movie. They are both very similar but I cant explain without spoilers. Enjoy!