I'm not touching the chapter thing, but I'll bite on the region bit.
For Delta, from our national website:
"Alumnae Deltas comprise the largest proportion (76%) of the membership. The largest segments of alumnae Deltas are almost equally divided among three of the seven regions, Eastern (21.8%), Southern (21%), and South Atlantic (20.5%).
Undergraduate Deltas comprise 24% of the membership and have the largest segments of their members in the Southern (23.6%) and South Atlantic (22.7%) regions."
For OPhiA, you can look
here on our national site and see that we have the bulk of our chapters in the South.