We had already decided and discussed in that thread you're talking about that if they are
currently releasing solo music while not being under a korean label, not singing primarily in Korean, and based in a country other than Korea, they are an international artist currently regardless of where they debuted and if it was under a Korean label
Since Yuqi's cards were made while she was under a korean label she is in the Korean deck regardless of them not being in Korean (language). Since Tiffany is active as a soloist in the US, singing primarily in English and not under a Korean label, she is in international
Everglow is primarily active in Korea so if Yiren released a solo while still being primarily active in Korea, under Yuehua, she would be in Korean
As Tiffany is currently an American soloist, she is in the international deck, tho she was formerly a Korean one
cross-label groups (where one label is not Korean) like WJSN with Starship X Yuehua would probably have the members solos in Korean deck as long as they get cards while still an official member of the cross-label group, but cards team will discuss