Being a multifandom stan, I got to know many different ones, with their good and bad sides, so according to this, my favorite ones are:
1. Carats
2. Monbebes
3. Ikonics
They help whenever they can and are always up to talk calmly. Carats and Monbebes also have such a beautiful friendship, just like their idols! Ikonics have a special place in my heart since they helped me a lot when I started to get into kpop, so maybe I'm a little biased~
Anyways, I feel like fandoms from underrated and/or older groups are the best, or at least the most respectful.