Follow Your Heart is an original screenplay (not an adaptation) that is an easy, light, and heart-warming Rom-mystery-com. It's a leisurely paced drama (imho, they could have tightened it up by about 4 eps) with strong acting, great fight choreography, good OSTs, and lovely chemistry between the leads. It's not perfect, but as someone who rarely re-watches dramas I could actually see myself wanting to rewatch much of this for the cute humor, the sweet romance of the main cp (ugh the way he looks at her even though he can't see her face! this is true love!), as well as the action, and great performances - the ensemble cast is very strong. From the many Yan Nanxing 'shapeshift' actors, to the support characters, and especially Jiang Xinbai's extra af mom who I thought was hilarious.
If you missed it when it was airing and you need a comfort watch, look no further.

-spoilers below-

First up: Happy Ending for all, except some side characters who sadly leave us but give our leads the opportunity to cry movingly. Even more joyous than the final wedding scene for me is the scene where Jiang Xinbai finally finds Yan Nanxing - even though she is self-conscious, looking like an old woman, afraid that she'll never turn back to her real appearance, he truly sees her and loves her as she is. This is the Real Thing folks.

Weak points/disappointments: the pace lags during the middle/last third, and the main lead's story disappears for a while. This definitely affects our appreciation of their chemistry, which is so strong at the beginning, but then we rarely see them together! LYX was injured on set so that's part of it, but I think the writing is more to blame.
Though there is one main "case" that is being solved throughout the whole drama, and one main cp, significant time is spent on the side-plots for the two other romances in the drama, of which at least one was not necessary. Characterization of some characters - particularly Jiang Suoluo (Sebrina Chen) never really worked for me. She was supposedly brilliant and competitive with her brother, but somehow couldn't even figure out how to break off her engagement to slimy social climber Yan BiQing (who did a great job of making me hate his stupid face.) I never got over how annoying I found her at the beginning even though she reconciled with her brother. The romance between her and Ruoqian felt forced and artificial for me - it would have been much more satisfying to see them crush on each other slow-burn style but then go off and become the great Chancellor and official that they wanted to be. Cdramas please stop making the end game early marriage and babies for EVERY character. JUST STOP.
I was also disappointed that they seemed to weaken Yan Nanxing in the middle - she is a traveling doctor who knows martial arts! She's a wily girlboss supreme! If they needed to make her a bit more helpless to further the plot they could've done it by putting insurmountable obstacles in her way instead of just somehow making her less competent. I still love her though. YNX is now one of my favorite FL characters, and I am so so so happy for Song Yi that she got to play her - she did a fabulous job.

The good stuff: Jiang Xinbai and Yan Nanxing are great characters, played by great actors, and their chemistry is great. Their relationship is a series of green flags, no contrived misunderstandings, just mutual admiration. The plot device of JXB being face-blind and her shapeshifting is adorable. He recognizes and loves her no matter what she looks like. This was especially funny on the 2nd wedding night - his was so angry he wasn't going to get his wedding night funtimes. And it was very touching at the end, when he recognized her even though she was old and gray (particularly touching to me, an old and gray watcher.) This is what love is like.
I did enjoy the Shang Beili and Tong Sai'er relationship as well - it's cute that he falls for her and her unconventional cooking then gets gege-zoned. Huang Riying did a nice job of playing a broadly humorous but innocent and naive character (which is tough to do, I often find these naive girls irritating, but I just thought she was cute and funny.) It was nice that they got Shang Beili to stop shouting so much after he fell in love - it softens even the loudest general I guess. It was also so satisfying to see the JXB/SBL relationship go from enemies to bros who had each other's backs.
I love love loved all the actors who played Yan Nanxing. Even Cheng Xiao who I have not been impressed with in the past did a great job of picking up YNX/Song Yi's mannerisms, and playing a woman stuck in someone else's body. Extra special shouout to Wang Chengsi, but all the dopplegangers were great.
Loved loved the appearances by Zhao Yuanyuan (Love is Sweet with LYX) and Wang Yifei (Ashes of Love & TTEOTM) give these beautiful and talented ladies some leading roles please!
Last but not least, the moms! THE MOMS. Finally we get a LYX drama with alive moms, and they are both tough, funny, and thoroughly entertaining. YNX's adopted mom was streetwise and funny (though i wish she hadn't randomly disappeared through some eps) and JXB's mom was a highlight for me. Weng Zhenrong did a great job being thoroughly entertaining - the Duchess was competent but capricious, intelligent and politically savvy but also loving and devoted to her kids. Her portrayal really encapsulated the kinda screwball-comedy tone I thought they were trying to go for, but alas, the entire drama didn't stick with that tone.