Female Assassins and Can't Buy Me Love have royals.
Perfect Couple she grows up a commoner, disguises as a princess to find someone she is looking for and I forget who she actually is because it's been so long. She might have been one of those "lost" princesses but I could be wrong. She grew up a commoner and always thought she was.
King is not Easy she's a commoner looking for marriage to a sexy guy and when she literally spots one on the streets, she finds out who he is and joins the palace maids to get close to him. She's pretty upfront about what she wants. She body swaps with the emperor.
Queen of Diamonds and Hearts both the wives are commoners. One is bad. One is righteous. It can be frustrating to watch because she saves him and his kingdom over and over again because he's pretty dumb and arrogant. He's obsessed with his second wife and her physical beauty. He eventually sees the light and falls for the original wife with the birthmark on her face.
And of course there are two series on Mulan and they had to both be made in 2013 to confuse us:
Mu Lan
Legend of Hua Mulan
In both instances the Rouran prince falls for them. I think the second one I linked she likes him as well.
Some Korean stuff:
Sungkyunkwan Scandal, I believe she writes and illustrates naughty (sexy) novels and then ends up disguising as a man to write a 'national exam' test. I honestly forget how bratty she is, if she is at all. She's trying desperately to survive in a world where she's not supposed to be able to work or be a scholar. The prince and heir to throne falls in love with her along with a bunch of other noblemen.
Love in the Moonlight is similar to Sungkyunkwan Scandal where once again a girl struggling to survive dresses as a man to accomplish things.