The creators made the character in response to a question posed by a fan of what Adora and Catra's kid would be like, is the short answer. Whether or not that makes it canon is debatable.
She hasn't confirmed this is actually her, but given that it meets all the hints she's given, and the writer hasn't written anything else before or since, even after getting a billion views, means it's most likely this one.
Most of the ships in Overwatch are pulled from a hat. PharMercy is almost entirely because they make an effective combo with Pharah's jets and Mercy's glide and tether. I'm still waiting for my Orisa X any other character ship
Yeah, it's always odd to pick a setting if you don't plan on using it. I love Touhou, but it's not like this needed to be Meiling. Could have just been a random person in a random setting.
@bojack Kyoani was attacked, a man blocked the exits and set fire to the building. I'm not sure the final count, but upwards of 30 people, or one third the total staff, were killed in the fire.
I'll admit, I never really figured out the relatonship between Seija, Tojiko, Futo, Miko, and Hijiri. That whole aspect of Japanese culture is just totally opaque to me.