I give consent. I'm really interested in this as FE fan, and as one who's taking the time to learn Japanese after how badly some some localizations have been.
Okay, first off the game uses Buddhist symbolism. Your avatar's personal class of Enlightened One? That's called Nirvana in Japan, which is supposed to be a state where someone extinguishes the three flames/poisons of greed, hatred and ignorance that plague humanity. The empty throne we see on the title screen, that's a Buddhist symbol associated with lions and deer. The flag you get in SS and VW is based on the Banner of Victory, a flag used to symbolize Buddha not falling to the temptation Mara's daughters and obtaining Nirvana as a result. That flag is, according to the creators in the Nintendo Dream interview released just after the DLC came out, the game's Fire Emblem, not the Crest of Flames that is possessed by Byleth, Edelgard and Nemesis.
In Japan, Crimson Flower is called Safflower. It's a very specific flower. Unlike the red rose mentioned in Edge of Dawn, which simply means love, a safflower means attraction. You find something attractive, and when you use it in a bouquet you're saying "I'm trying to catch you/good luck (usually with regards to marriage)." There's a difference between love and attraction, especially when the game is using the aforementioned symbol of the Banner of Victory.
The devs admitted they expected players to pick the Black Eagles first (and they believed most players would only play one route), and they also wanted to play a trick on the player. When joining Edelgard was too hard and the test players couldn't do it, they made accessing Safflower easier. This is in spite of them saying they wanted players to immerse themselves in Fodlan, and that Fodlan was built to support Silver Snow's story. Take all this into account and it paints a picture of Safflower, the route which ends with Byleth losing their Enlightened One status, as the route of ignorance. If Byleth actually fights Dimitri in the penultimate stage, he will call them out on walking down the path of the savage beast or something. The path of the beast in Buddhism refers to acting in greed, hatred or ignorance, the antithesis of Nirvana.
Safflower is the game tricking the player into siding the villain.
The devs also said in that interview that Safflower supposed to lead to what is known as Hadou, in contrast to Azure Moon leading to Oudou. This is based on China's Mandate of Heaven. Under the Mandate, the ruler is believed to have been given the privilege to rule by the Heavens and must act accordingly. They must put the people first, not rule in their own self-interests and instead rule benevolently. If they do so, the land will prosper. This is Oudou, and part of Oudou is overthrowing rulers who have fallen into Hadou. Hadou is a state where the rulers don't act in the interests of the people, are willing to sacrifice the people in order to get what they want, and enforce their rule through either political or military strength. They're rulers who lead with absolute power. The people are supposed to rise up against Hadou, rebelling against those rulers and overthrowing them is considered an act of justice.
Hubert's endings point to hadou, even in the English version there's confirmation of rebellions he's putting down from the shadows. Edelgard's endings also show her banning a play she hasn't seen, and in the Japanese she doesn't create a "free and independent" society. She creates one where the people are pushed to be self-reliant in spite of her whole "when people support each other we don't need gods" line in CF's final cutscene. Her pose in the painting at the end of the route is a direct reference to Napoleon's coronation portrait. complete with inverted Hand of Justice as she stomps over the flags of those she's conquered. The idea she's trying to become Fodlan's supreme ruler is also highlighed in the last chapter of White Clouds before going to Safflower, "Onset of a Battle for Supremacy" rather than power struggle, as well as her personal battalion. Her being referred to a Hegemon in Byleth's CF title, her Hegemon Husk form and Claude's comments to Hubert in Japanese VW (It's not "Your military rule ends here" like in the English dub), all signify this. Likewise, exploration dialogue also pushes that the army in Safflower are really keen on Edelgard unifying the continent under her rule, that she's starving her people to support her army, using Crest Beasts and that the people were against this war. She even takes control of the Church as revealed by a couple of endings.
Tying to the fact Safflower is supposed to be the route of ignorance, Edelgard is depicted more as a manipulator. Not only does she lie about Arianrhod, her story is contradicted all over the place. It's not meant to hold water either, as Silver Snow was the route the worldbuilding was done to support. As the player invests in understanding Fodlan, this should become clear. Safflower shows that Edelgard is a liar, a genocidal one considering her saying "Rhea and the Children of the Goddess need to be obliterated" in private right before offering Rhea the chance to surrender. A line in the Japanese confirming that Edelgard is manipulating TWSITD in Safflower was changed to them manipulating her, while the NPC talking about unrest in the Empire has the line about how this is calming down due to Edelgard's "information campaign" was cut entirely. Just that one sentence, the rest of the line is still in the English dub.
Edelgard;s voice acting sounds more harsh and mature than her Japanese counterpart, which kinda ruins the effect. We're meant to be taken off guard by what she's doing and saying, not by her cutesy moments. Similarily, Rhea's VA was told to act unemotional with a burning rage under the surface, compared to how her Japanese counterpart sounds like she's breaking down as you progress through Safflower.
There's other changes to the script. Dorothea doesn't sound as desperate in the English version, and we had Bernie tied to a chair by her father before that was changed to something more accurate to the Japanese script (which caused people to cry censorship). During the Holy Tomb in Japanese Verdant Wind, Edelgard makes it clear she intends to use the Creststones not destroy them. Also, Claude admits he doesn't like her in Japanese. Ferdinand fighting Hubert outside of Safflower went from "I will remove her from power, even if I have to lay down my life to do so" to "It doesn't matter what I think, I have my orders." Hanneman's description to Dorothea about what the nobility was originally supposed to be went from "people with knowledge who seek more knowledge, while guiding and protecting their people" to "the nobility was supposed to be a meritocracy."
The English script downplays the subtext, and alters lines to make Edelgard seem softer than she was intended. The game wasn't meant to be some morally grey "everyone's a hero in their own story, it's all a matter of perspective" sort of deal. Edelgard is meant to be the villain even when you side with her. She's supposed to be so stubborn that she doesn't get character growth, if anything joining her is meant to make characters into worse people (comparing lines between routes), and is supposed to be the same in Safflower as she is in the other routes. When she tells you the story, it's not the truth. It's just what someone who is a demonstrable liar is saying is the truth. She's supposed to be immature and genocidal. She's not supposed to be the good guy.
Edelgard's most die hard fans hate this. It tells them that they were wrong, that they didn't understand the game, stories or characters. Dimitri, Claude and Rhea are all made out to be good guys, while Edelgard is singled out as the bad one contrary to what Crimson Flower said. Edelgard isn't the sad, innocent victim they wanted her to be, nor is the world she's fighting for one we should support. Siding with Edelgard isn't about free will, it's about Byleth being led astray. You get the idea. This is why they keep claiming "death of the author" to erase canon and instead replace it with their own fanfics, sorry, analysis. Stuff Edelgard does in canon, they argue she doesn't. Dimitri's mental illness is erased, instead his arc is about overcoming toxic masculinity...and he's still not a good guy because he's crazy and will pass on his craziness to his children. Claude's arc isn't about him learning to trust people, he's just using them and is the real Imperialist. Etc.