Here's a YT compilation of the English voices in the playable demo of Fates:
Part 1
Includes Azura, Camilla, Takumi, Kaden, Kaze, Hana, Nyx, Arthur, and Beruka
Part 2
Includes Selena, Rinkah, Sakura, Saizo, Subaki, Hinoka, Leo, Scarlet, Ryoma, Niles, and Odin
Part 3
Includes Felicia, Effie, Male Corrin, Mikoto, Xander, Yukimura, and Garon
Obviously it isn't much to go on, but you can get a decent impression of how they all sound.
I like most of them, but dislike others. I don't like Camilla's voice at all, I don't like Nyx's voice (although I guess it fits), Felicia sounds too bored and old, and Hinoka just sounds terrible. Sakura also sounded really old, and I feel it's a bit unfitting.
Leo and Takumi both sound great, I like Ryoma (someone said that Matthew Mercer would be voicing both Xander and Ryoma. I wonder if that's true, though, as Xander sounds really different), Rinkah, and Arthur (it's so perfectly cheesy).
This actually makes me wonder if Odin and Selena have their original voice actors from Awakening. Selena doesn't have many lines, but from what I've heard of it, she sounds very "off". Odin sounds kind of unrecognizable compared to his Awakening VA. Because of this, I question if Liam O'Brien will return for Laslow. Personally, as I mentioned, while I love Liam O'Brien, I feel like his voice does not at all fit the character.
Overall, I guess the game sounds... Fine? Not great, but not terrible either.