Recommendations

Both shows about female leads who are insecure about their looks but the male leads help them to be more self confident:
-In true beauty the female lead has a problem with her appearance, so she put makeup to be accepted in society.
-In weightlifting, the female lead thinks that she lost her femininity by lifting barbells.
In both main male leads have dark secrets past but are nice.
Both include love triangle, friendship and college/school theme.

1) Both are censored same-sex dramas
2) Both are of the xianxia genre
3) Both have two males as leads
4) Both have a bit of mystery and wuxia
5) Both are adapted from boys' love novels.

I know the dramas are kinda random, but if you came to see Iljimae to see Kim Yoo Jung in her child actress days, then I definitely recommend you at least see her scenes in Grudge the Revolt of Gumiho. It's her first lead role in TV. If you see her romancing Yeo Jin Goo (her lover in Moon Embracing the Sun) in Iljimae, definitely check out Gumiho Fox Child for her romance with Lee Tae Ri (formely known as Lee Min Ho born 1993, he's another lover of Kim Yoo Jung in Moon Embracing the Sun).
In both dramas though, Kim Yoo Jung plays a good kind hearted girl. There are also a few scenes in both dramas that are quite similar. In Iljimae, Kim Yoo Jung enjoys the company of a bird while in Gumiho Fox Child Kim Yoo Jung enjoys following mostly fireflies and sometimes butterflies. Another scene is where Kim Yoo Jung is helping one of the young male characters heal their wounds. And another one is where Kim Yoo Jung's adult version Han Hyo Joo is enjoying the lanterns while being watched by one of her love interests in Iljimae is similar to Kim Yoo Jung in Gumiho Fox Child where she was also watching the lanterns while her male love interest looks at her so lovingly.

=> There is a prophecy in both dramas about "two suns cannot exist in the same sky"
=> Same child actors of the 2 main leads which are Yeo Jin Goo and Kim Yoo Jung (personally I don't ship the two former child actors unlike many but it's still interesting too see that their only scene together in Iljimae is so similar to their first meeting in Moon Embracing the Sun, falling petals also feature in some romantic scenes of them both in both dramas).
=> Two half brothers who are rivals for almost everything, half brother envies the male lead for the attention he has with his parents (or their foster parents in Iljimae), to everything the male lead has compared to the half brother, to the female lead that loves the male lead over the half brother (interestingly, the male lead in both dramas are both the younger half of the two brothers and also also the sons by the legal wife of the dad).
=> Eunchae's good heartedness (female lead in Iljimae) reminds me of Yeon Woo (female lead in Moon Embracing the Sun), this is especially true with the young Yeon Woo (Kim Yoo Jung). Han Hyo Joo and Kim Yoo Jung are so in sync with each other as actresses and are really good in playing these beautiful kind hearted noble girls that every male lead likes. (I personally feel Han Hyo Joo would have really rocked the role of Yeon Woo, Yeon Woo with her memories is especially so similar to Eun Chae).

Princess Man is the sequel to Tree With Deep Roots (not the same producers, but the kings in Princess Man are the ones that follow the kings in Tree with Deep Roots historically). There are fictional elements in both dramas, but at least the names of the kings and the ministers are all real people. Tree With Deep Roots tells some parts (although some may be fictional) of King Sejong's accomplishments and on how he created Hangul, Korea's alphabet. It started with the reign of his father, King Taejong. Princess's Man, tells the story of King's Sejong's sons King Munjong and Grand Prince Suyang and what will eventually happen to their families. Han Myung Hee (a character that features in Princess's Man) also appears as a minor character and is mentioned by name in Tree with Deep Roots.

Both dramas feature Moon Chae Won in hanbok (where she looks extra pretty). Even though her role in Painter is only minor, it's still worth watching because it's her breakthrough role and her role in it is so unique. She has chemistry in her partners in both dramas that led her to win best couples with her respective partners. Both dramas are really great in general (in fact both were nominated for Baeksang). As of February 2, 2021, these are also the only two dramas that got MCW to be nominated at Baeksang Awards.

Both dramas are set in the Joseon dynasty. Villains in both dramas are kings (or will eventually become King in Princess's Man). Both main couples in both dramas are kind of "Romeo and Juliet" since the parents of the female lead is an enemy of the male lead (though there is less focus romance in Iljimae). Park Shi Hoo features in both dramas.

Similar stuff FL travels into a story and messes with stuff. It was a good watch. Haven’t seen much of “oh my drama lover” though.

Same ML, and mostly same plot. However, the ML's fiancé is 'killed' by the FL, and he blames her. The FL's father is obsessed with her, and he actually drugs her that night. It's a story where he seeks revenge, and she seeks justice. He sees her true self, and they slowly fall into love with each other.

I think it's similar because it says that Xu Nuo and Ke Si Yi share the same emotional state just like Eun Gye Hoon and Noh Da Hyun in this Korean Drama

Both are mature dramas for an older audience , they both deals with affairs , darker themes and really well executed ,good pace and so catchy .

Love & ? is about 3 orphans who grew up together and then two of them get together. Go Ahead is similar, 3 neighbors/family grow up together, and two get together later.

Both:
- abandonment issues
- are really relateable

I really enjoyed both. Don’t let Love&Pi’s rating dissuade you, it deserves wayyy higher than what it has and it’s really good

Both dramas have as their story a group of people who conduct human experiments. In both dramas people escaped their facility and developed superpowers. In Luca and in Awake those children, which were experimented on, hold the key to the success for this experiment and are therefore wanted and hunted.
Truly it feels like the exact same story just different characters.

While A Girl Like Me is much lighter than The Rebel Princess, both stories are focus around the strength of the female lead. Both FLs are close family to the emperor who tends to favour them as a young girl in the family. Emperor indulges both FLs to choose their spouse, in both cases they actually end up choosing someone strategically but it is a love match. Both shows are about navigating political schemes which they just get caught up in. One has a mother who is a princess and the other a grandmother who is a princess. One has a ML who is the army general with military power and the other a close advisor to the emperor with political power.
Girl Like Me has a romcom feel whilst Princess has a dramatic feel.

Similar positives vibes while watching it from start to end . Kind of same cute office romance like here ....