The Sources I use are almost always through kprofiles.com
I absolutely love the set up of everything and it is so easy to find everything.
If you plan to write or are writing, definitely use this site because it is not only confirmed info but it is written by fans. I always find little things that I don't know about the group and they often have silly things in the profiles as well.
Also, this is not sponsored. I just really like the site.
ATEEZ:
kprofiles.com/ateez-members-profile/
Stray Kids:
kprofiles.com/stray-kids-members-profile/
A.C.E:
kprofiles.com/ace-kpop-boy-group-members-profile/
MCND:
kprofiles.com/mcnd-profile-facts/