One interesting Arknights fanfic could be those that explore the backstories of the operators in more depth. For example, a fanfic might focus on the early days of Amiya's leadership and how she coped with the various challenges. Another type could be the ones that create alternate universes where the factions have different relationships. Some fanfics also center around the relationships between different operators, like the friendship or potential romances.
The determination of the real protagonist in the Arknights event story is subjective. Different players might consider different characters as the main focus based on their actions and influence on the story's development.
It's mainly because fan art often involves visual reinterpretation and can sometimes fall under fair use, while fan fiction typically involves extensive use of the original story and characters, which might infringe on copyright more easily.
Fan art by Sarah Tregay is likely to be artworks created by her in the context of being a fan of something. Fan fiction, on the other hand, is fictional writing by fans based on existing works. For example, if Sarah Tregay is a fan of a particular book series, her fan art could be illustrations of the characters or scenes from that series. Fan fiction could be stories that expand on the plot, create new adventures for the characters, or explore different relationships within the world of that book series.
Yes, they seem to like fan - made art. They often share and respond to fan - made art on their official social media accounts, which shows that they appreciate the efforts of their fans.