TIL first person tui vs mình ở Sài Gòn

Apparently they're congruent but tui is more popular these days and now the convention is to use mình sometimes with your partner. But you can still go around using mình and be fine. But since it's less often used it can sound just slightly more distant. Because the South prefers friendliness.

Update November 26, 2023: So turns out that you're never supposed to use tui, it's a kind of thing that the Mekong Delta people use. You can use it in colloquial with joking with your friends only, but never in writing.