there’s a setting on the groups page; “Who can see this group”; if I set that to public; my group messages will still be hidden right?
Yes the category security is something different.
All this means is that people can see the group exists on the group page here: Discourse Meta
They can also see who is a member of it etc.
It might be worth adding that the setting “Everyone” has a different meaning depending on whether the forum is public or private. In public forums “Everyone” basically means “the whole world”. In a private forum (i.e. which require users to login to see anything), it means “all logged in users”.
See also:
신뢰 수준 1에 40명 남짓한 멤버가 있습니다. 그룹 가시성이 '모두’로 설정되어 있지만, 멤버들이 서로를 볼 수 없습니다. 그 이유는 무엇인가요?
이것은 자동 그룹입니다. 자동 그룹은 수동 그룹과 동일한 규칙이나 동작을 따르지 않습니다.