I picked “horror/mystery changes depending on the romance route,” but more along the lines of: the main story is the same (say, it’s always a cult) but the details of the horror/mystery change depending on your RO.
So like, maybe one RO is actually a cult member, so if you choose their route, you learn more about the inner workings of the cult. But if you choose the, I dunno, detective RO, you would be doing more investigating with them, but never get the ‘insider edition’ on the cult. Basically the main mystery/culprit is the same, but maybe how you discover/learn/interact with the culprit is different depending on the RO because each RO would have something different to contribute to the story.
I hope that made sense? I tried to put examples to help clarify, but it was difficult to elaborate in words haha. I also really like games like this because then your understanding of the story evolves with each character, and encourages replayability without making each route wildly different (e.g. different culprits for each route)
edit: I realized it’s just what Eiwynn said; she was very succinct where I ended up rambling haha