This is about asexuality, not aromanticism, but I believe you would be interested in this video essay:
I definitely headcanon her as aroace, and there are defnitely some amatonormative themes in the Barbie movie.
I think the times he 'acted' allosexual was more so him just trying to fit into a role, a big part of his arc is his identity being completely tied to relationships and not having anything beyond that, so it makes sense he would try to cling on to anything, including a false sense of allosexuality. I definitely think Ken is ace.