get rid of toggle in choice interface

Not 100% sure this is what you're asking, but could the "choice_style": "multiple" do what you need?

For your other question:

In theory yes, that's correct --- that's how the model works, although we haven't tested this well with a choice interface for textcat. So if your results seem to not make sense, it's possible we have a bug in the data transformation around the multiple labels.