Hanayo’s and Ruby’s voices are very similar, it’s the matter of pitch both cute and both childish.

Hanayo as three types of voices, one of them is fluffier and very airy, so basically her cutesy and happy voice that she normally uses in μ's. The second one is a sad and a bit stronger type of voice, Shikaco’s real voice (Hanayo’s voice actor) She uses this voice in Love Marginal and some other song out there…And Hanayo’s last voice is more deeper and stronger, she sounds like Maki she sounds like this in WILD STARS

Hanayo’s example video! https://www.youtube.com/watch?-Nrwnc&&-nIqcNg-PZkXOXe8TRWShB65

Ruby’s voice is the most easiest to identify out of Aqours, her voice is high pitched and very childish like Hanayo’s cutesy voice just turn it up 50% more cutesy and childish, and her voice gets more childish in Genki Zenkai Day Day Day. Do your Rubesty!

So high pitched and cutesy for both of them!

Ruby example video! https://www.youtube.com/watch?