There are not hierarchical permissions in NodeBB. If you would like to see hierarchical permissions, you could open an issue on our Github page and request such a feature.
I do believe we have a way of copying permissions between groups, so that could help you out in doing what you want.
Hmm that would actually be a good fix for this here: https://community.nodebb.org/topic/6582/cooldown-on-group-join-requests/1
either translation issue or just a typo. reporting regardless 😉
Ah, well spotted, thanks for reporting 🙂