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1 or 4 feel like the best options here for Misaka. Raijuu for the obvious lightning-related reasons, and Kitsune for being elegant and sophisticated like the stereotypical student from her school.
"Kitsune as the elegant one" makes it a better choice for Misaki, Junko, or Mitsuki though. 1 is the obvious choice for Mikoto.
Kuroko's monstergirl form is just as obvious as Mikoto's: Demon. She'll be the one who purposely spreads the infection as far as she can.
Becoming FROGGË is the option for her to be happy about this, lol