If you are looking for S-tier Cryo DPS characters, then by all means, go with Kamisato Ayaka or Ganyu. I would prioritize Ganyu over Kamisato Ayaka because of her ability to deal massive charged attack damage. Ganyu is the definition of an overpowered character in the game's meta. As for Shenhe, she can buff your characters' damage, which makes her a really good supporting character. Ultimately, it's up to your team's requirements to decide which character to use to help them fill a certain role.