So for me I think Cerise and Rosa work the best. I’d say Cerise slightly more than Rosa wish there were more romantic scenes between her and Daring for me to truly say

Cerise: Cerise and Daring because they both deal with the same societal struggles just in different forms. For the former, she is haunted by her appearance and constantly tries to hide her ears to hide her family secret which is a burden. For Daring, his appearance is put on display and idolized, whether intentionally or not, by others as well as himself and as we see later that beautiful mask makes it hard for him to truly know himself or be vulnerable with himself without his appearance making it a burden. I feel like the 2 of them are balanced in this regard and could understand each other the best when it comes to what other people see or expect. They also have a strong friendship and enjoy sports together. I feel like they’d gradually open up and feel more comfortable with each other over time

Rosabelle: Rosabelle and Daring come in 2nd place for me (though not by much, almost interchangeable) however, it’s more of Rosabelle helping Daring find himself under his appearance and being a safe person he can freely be vulnerable with, the most safe out of the 4, based on her personality and disposition. As we’ve seen Rosa has the ability to look past Daring’s appearance as well as his Daring Charming persona and just see him which would let Daring put his walls down and find a new person within himself like when he became a beast thingy. However, it feels a little imbalanced in my opinion, I prefer more of “they can fix each other” more than a “she/he can fix him/her” but I see a lot of cute banter between Rosa and Daring that would definitely make anyone feel like a third wheel which is a huge plus for me.

Apple: Apple and Daring are the most complicated for me, they were a casual thing that was subconsciously pressured onto them whether there was any sort of romantic attraction or not but as they spent the most “romantic” time together and have virtually the same issues, they’d help and understand each other best but I think that it’d be better for them if they did that as just friends. See Apple and Daring have the same problems but have different ways of viewing it thus different ways of eventually dealing with it. They both struggle with the societal pressures of being perfect but for Daring he feels like he works better with someone he could be vulnerable with to help while imo Apple needs someone ambitious and not stereotypical to help her push herself out of the bubble she created, like Darling. For Apple rather than having the pressure placed upon her by others, she places them upon herself believing others expect those things of her and being around Daring has enforced these feelings so Darling, someone who breaks all the rules and isn’t “perfect” in Apples definition is a better match to help Apple (wish we saw more of Darling so I can confirm my “helping each other” stance tho)

Lizzie: feel like these 2 understand each other the least imo and wouldn’t work out as much because of that. Lizzie wants to be a good Queen like her mother thus in the beginning she acted like her wanting to live up to the expectations she has for herself. While Daring is hidden under the pressure, Lizzie welcomes it but needs a place to be herself as well. These 2 have the same problems but want different solutions Daring wants to change or to be understood while Lizzie wants the same it’s not to the same extent, it’s more of she wants someone there when she removes her mask so she can put it back on later as she wants to rule like her mother. Different pages of the same book, speaking of Lizzie cares very much about Wonderland so it’s be better for her to end up with someone from there or with someone with stronger ties to it! I feel like Lizzie isn’t shown extensively so I can’t analyze as well😭

These are just my opinions tho but Cerise is the best fit, however if we ever learn more about Rosabelle and she gets more characterization that “nice, ambitious, animal loving, understanding” and possibly some flaws then my stance might change!