Would I be better auditioning for JYP, YG, DSP or SM Entertainment?

I actually recommend that you audition for every company that will let you and that you would feel comfortable working with. So far, no company has debuted anyone of African descent who is not also of Korean descent. I have heard rumors of one company having a Black trainee, but so far I haven't seen confirmation of it. It's possible that Korean entertainment companies are not accepting non-Asian trainees. However, it is also possible that they do accept non-Asian trainees, but few people have scored high enough to be contracted and none have made it to debut. Much of the information being spread around about auditioning is anecdotal. Without concrete evidence of the judging criteria, you will have very little idea if you're "doing it wrong". You should build your audition based on the rules the companies provide and the experiences you've had in your previous auditions (for modeling, singing, dancing, whatever your talent is).