This is something that has puzzled me ever since I got involved in the bra blogging community. People say that Freya has narrow underwires, and that Fantasie has wide ones (some people say Fantasie is moderate.) I have never, ever found this to be the case. The Freya bras I have tried have all had wide underwires, much wider than the Fantasie bras I love.
With regard to Fantasie, some styles have wider wires than others, and I do think the wires get really wide when you get up to an H cup and above. I think that Freya, in spite of the idea that they have narrow wires, is really all over the map. A quick scroll through the Bratabase shows that Freya bras of the same size, but different styles, can have widely varying width of wire.
So, I don’t think it is really accurate to say that Freya is a narrow wire brand. It is a brand that makes lots of bras, some narrow and some wide.