"Hear, hear!" A round of applause for Janet, please! That is about the best illustration on voice training I have heard so far. I have a wee bit of trouble differentiating between inflection and pitch but the way you describe it sounds about right to me.
There is no need to feel intimidated with the idea of voice training. The idea and requirement at the beginning is to train your voice to be more in character with who you are, the you that you present, a voice in the beginning that is easy to adapt to and you feel comfortable with. If you wish to improve on it later, you can do so at your leisure.
As Annwyn said, it does appear that some African American women have a deeper almost male pitch quality to their voice. You will find the same with North American Natives, Italians, Scandinavians, and in some other Caucasian women. In most cases you will find they are rather, "ahem!", generously-proportioned women. But it's not necessarily always the case. I would have to say there are inconsistencies in this theory. "Hey, Ma!" "Too many holes in the canoe, I'm afeered one tomater can will never keep up."
I have also known women my size and smaller who have deeper voices than I. My ex sounded like a lumberjack compared to me, and swore like one too, so there goes that theory about women not swearing as much as the guys, well in part anyway. But I do believe on the average that women seem to be more respectful of how they speak in public places. The deep voice maybe is a hereditary thing, I cannot say with certainty.
Whether inflection or pitch, I would describe my voice before I started any training as one of those half way voices, like if the person I spoke to had their back turned to me, they would address me back as ma'am, until they turned to look at me, same as on the tely.
So with that advantage in mind, there was not much adjusting to do to allow my voice to sound more feminine.
The screaming? I can't really explain that one, I never practiced it, it just came out that way. Maybe it can be attributed in part to 9 years on HRT and having trained my voice to sound more feminine, or at least above my natural voice. My new voice after nine years, I suppose, would become my natural voice. Oh well, if this post is as clear as mud then you have my permission to make mud pies.
Cindy