I have a couple A/B/O fics haha, but here’s my thoughts

Nayeon - Can be Alpha or Omega but she’s a brat either ways
Jeongyeon - Could also go either ways but I like her as a beta because she’s very calming to me
Momo - Loser Alpha #1
Sana - Loser Alpha #2, though she can also be Mean Alpha, Bratty Alpha, Cute Alpha, you get the gist
Jihyo - Alpha or Omega but boy would she be a feisty omega
Mina - Alpha or Omega but i loveeee making her a shy quiet alpha :3
Dahyun - I’m so sorry I can’t see her as anything other than beta… maybe omega like 2% of the time
Chaeyoung - Omega… cannot be anything else. Omega.
Tzuyu - Also omega but very blunt and doesn’t care how she comes across