Or a combination of the two, I haven't watched the whole movie yet, but the two main characters Pokemon are Ash's Pikachu, and an Evee. But they also talk about Zeraora in the movie as well, so is it both?
Zeraora seems to be the main focus. In the movie, it has an enormous plot difference. Eevee is not very common in the movie at all. In addition to this, to advertise let's go pikachu and eevee, they would have made the movie in kanto, when it is in Johto.