I think you could translate backcountry in the Revolution Days as settled frontier often bordering Indian lands which included mountains, Piedmont, and also some Coastal Plain but by the Civil War, the hilly Piedmont was pretty well settled at least relative to the mountains.
Interesting about the Jeffersonian versus Jacksonian politics. I read a history of Davy Crockett awhile back and recall that Jackson and Crockett both gained their political power by appealing to backcountry settlers many of whom wanted resolution of land rights which were tied up in politics not to mention legal chaos caused by unscrupulous and crooked land speculation.
The sectional differences you mention for Alabama also existed for South Carolina and Georgia. Do you know how local representation worked at the state level - was it based on population and did slaves figure in to the apportionment equation?