I think Su Luxia's going to win by conquering the other two men - I mean what's done is done, his affection level is already at 100. It also just seems... a bit unrealistic (?) if our MC won over all three men in that world
For me the main difference between their approaches is that Nanako always tries to seduce them with her body, while Su Luxia plays with them psychologically. She really doesn't want to touch them or have sex with them and always tries to keep it clean
I'm sure at least one of the other two guys is a stoic person (like those germaphobic, black-haired isekai dukes) who doesn't like touchy women, in which they'll start disliking Nanako