In answer to the question "Is R&B more to do with Northern Soul or more to do with R&R", and without going off on a tangent trying to compare like for like and ranting on about likes and dislikes of either, (IMO) R&B has more to do with Northern Soul than R&R, as R&B and Northern Soul was predominantly performed and appreciated, on the whole, by mostly black Americans, whereas R&R was mostly more inclined towards, and more likely appreciated by, the white Americans. QED!!!
I hope this does not upset or insult anybody, as that is / was not my intention.