Alright let's be real, these character voice previews are shit, but I don't think we should be worried.
The fact they use shitty live 2D and basic lines, which don't even show off the girl's character traits and personality, kind of shows that these don't represent their voices in the anime.
I feel like they slapped these together and just asked the VAs to deliver a basic genki voice, nothing in character at all. I guess for animeonlys, not spoiling character personalities is fine and all, but what animeonlys would be stalking the twitter for this even.
It's a stupid decision and just pissed off primaries, but I don't think there's any need to get worried.
In this https://www.youtube.com/watch?v=im3k9VYR8AQ
Ayaneru does a good, in character voice for Nino. It's miles better than her shitty preview.
Even Miku's voice sounds off and too geki, it isn't deadpan/kuudere enough. While in the vomic Ayaneru does a good Miku voice, so it's obvious that they know what the voices should be like.
If the anime has fucked up voicing and they aren't in character at all, then yeah it's time to panic and trash this shitty adaptation.
But really, the fact Miku and Nino both have good, in character voice work already done in the past, shows that they at least have some idea of what they should sound like. The fact they aren't in character for the previews is just a bad decision.
If we get a kuudere voice like in the vomic by Miku's VA, it should fit well. Also a good tsun and condescending voice for Nino, like what Ayaneru does in the vomic.
I they ignore the vomic entirely and fuck the voices up then yeah, it's shit. But for now I'm going to without hold judgment until it actually airs. The live 2D is just another example of how the previews are not what we should expect from the anime.