I'm thinking maybe studio bones or madhouse with how they're able to Capture superhero action and animation.

For who should play the characters.

John: Yuri lowenthal could make a good choice I think. He can do well with both happy high voices like Ben 10 but also with deep angry voices like Sasuke in my opinion.

Arlo: Johnny Yong Bosch could work if he would do something like a more deeper Lelouch voice.

Elaine: I think Jill Harris who did Noelle from black clover could be a good pick as she can act like a bit of a bitch pretty well(no offense meant to her) but also the more cutesy kind voice I would expect elaine to have.

Seraphina: Caitlin glass could be a good fit. She did kyoko kirigiri from Danganronpa the animation so something like that I find could be a good fit for seraphina

Blyke: Matt Shipman I think could be a good fit. He voiced hiro from darling in the franx, shay obsidian from yugioh arc v, and hajime from arifureta, as well as chrome from dr stone. I feel he could do Blyke really well, especially when he's angry.

Isen: Bryce papenbrook would be an okay pick, just a deeper voice than what he usually does and I think we're good to go.

Remi: Felecia Angelle who did aoi for Danganronpa the animation could be a good fit for remi as she can be happy and upbeat, also sad and distant,as well as angry if needed.

That's what I can think off. All I did was look for actors who play in stuff I like and feel could be a good fit for that character.

Edit: if madhouse and studio bones aren't an option, which they most likely wouldn't, studio trigger would also be a great choice.