Are Korea and international mutually exclusive anymore?

Yes and no. Some groups have a matching popularity across the international and domestic markets, and some don't. Well, it's possible most do but there are some counter examples.

For example, it seems the big breakthrough Oh My Girl had in 2020 in Korea didn't rise their stock so much on the international stage. They're a top gg locally nowadays but I doubt they would have a matching touring power internationally. Same with Brave Girls and her unexpected rise to the top this year. I think Gfriend was also a group that was more popular locally than internationally.

I feel like the biggest groups are mutual, BTS, BP, Twice, those big popular groups, but others are more individual to areas

Back in the second generation being popular overseas means that the group was huge in it home country but things started to shift slowly when the 2.5 generation made their debut and it completely shifted in the 3rd generation Got7 and Monstax where one of the groupes who gained fame internationally first then locally.