When referencing "Asian" as an ethnic group, I think it's safe to assume most western people would generally picture East Asians. Yes by dint of sheer population and landmass that would probably imply "mostly Chinese" but also Korean, Japanese, Thai, Vietnamese, Mongolian and a whole bunch of others in that part of the world.
That said (and I may be misremembering here) I think they've said back when Rebels was on the air that the intent for Sabine and her family was for them to look Japanese, specifically. So that's probably going to dictate any casting for a live action appearance.