I think it's a good idea to have BUT should perhaps be limited to avoid spam and redundancy. If I was running this as a business on some level, I'd make it a VIP only feature. We don't need 15 groups for the same NSFW topic slightly worded differently again.
I don't think it's a good idea to have creators moderate unless your idea is to have private groups too then it's fine, otherwise it invites bullying and headaches.
As for general process, perhaps keep it simple, but for user created groups have a flag a group feature? Because inevitably someone will find a way to create a group based on an illegal activity or fetish.
I think it's a great thing to bring back but it needs a lot of control and may be very time consuming for you all.