From the art I've seen, her style for eyes look more elongated. The fire emblem characters have smaller and more emphasized eyes, which looks like one of the Atlus artists. This is why I'm asking for confirmation, since people seem to be basing their assertion on a Twitter post that just claims it's Chinatsu.
On formations, this is just me speculating but I think it could simply be this game's way of dealing with skills (along with combat arts). The triangle formation they showcased could be a Lunge-type formation, for instance, putting your army on the other side after battle.