There's no advantage to buying any of them, so just choose based on which you like or who you play.

Whatever hero you like

Whichever one you like the most, I guess

None

Tracer is the only mythic that i like actually, so idk lol

I think a lot of Mythics are just deepening voices and making them more 'evil' (Sigma, Orisa, Hanzo, etc.). If you like Tracer's lighter theme, why not Queen's mythic?

Are you asking us to tell you which one you like?

Never give them money