7. I think you could make a case for the FL of Memories of the Alhambra turning out to be a plot point. I know there's an acceptable amount of screen time given to setting up the relationship, and she does have some substance, tastes, and goals of her own. But overall, she reminded me of her identical twin construct inside the game - decorative context for the ML.
8. I'm watching Joy of Life 2 right now, and given the intricacies of the plot in this series, there are several characters who appear and disappear to advance the plot. I feel like they gave Teng Zi Jing just enough backstory and motivation to have him serve as a motivation for the ML. And now that I'm on part 2, they're getting more mileage out of his family!