Soulmate & You & Me & Me are similar as both are nostalgic movies, the female lead characters (you & me) are twin sister but best friends and liked the same boy (Mark) from high school. Just as Soulmate with the 2 female leads are best friends and like the same boy from school.
Both male leads kissed the other girl first. All 3 actors rode on bikes and hang out together.
Both Movies had a similar bath scene with the 2 best friends in Soulmate and 2 sisters in You & Me & Me. The baths looked identical with blue tiles. I watched soulmate first, but it felt like I was watching the same movie again at that bath scene in You & Me & Me. The similarities are insane as if the cast and crew flew to the Country the bath Tub was at.

Both Dramas have a strong leads want to be the best at what they do to take down the bad guys.
Both Dramas have politicians suspected of corruption
Both Dramas have public prosecutors but some take bribes from Business groups and having Assemble man controlling everyone so he can keep manipulating them in more corruption.
Both Dramas have the Assemble Man killing anyone in his way.

Its a romantic drama, both drama have ex partners appearing. Both ML are China's top tier actors, some mischievousness will happen E.g Brother adding "Married" based on the requirement to work at the Law Firm, Playing a game with your high school crush without him knowing then pretend to have issues with a purifier to get his attention ha!