Some of them are not even ambassadors because the brands don’t even announce and post about it. It’s just a partnership.
yes, i think there are different levels of partnership or deals.
Some are contracted for a campaign in an specific country, like a model, but of course the name or fame of the idols is what they are interested on.
Others are called for a photo shoot of a magazine with a brand.
And yes, of course there are also brand representatives, but are different levels on that too. For example, some from a country or region (like Asia) only. And there are Global Ambassadors. But there very little of those from Big brands. I think some companies like to use the word GA very loosely when in fact that idol is just a brand local representative.