I would be inclined to think that true throughout the south, not just in Texas. The aristrocrats and largest slaveholders tended to be the "old" money class who held the reigns of power. BTW, I only 'whip up" on the Slaveocrats like Davis who started that awful war. The rest of the southerners were victims of their corruption, greed and arrogance before, during and after the war and it mystifies me that anyone could admire men like that.
Well, yes, I was just sticking to my source, but yes, it would be fair to generalize more widely, and in fairness Fehrenbach has a longish chapter in which he describes the settlers of the Old Southwest and their long journey from Presbyterian Scots-Irish to largely Baptist Southerners and Westerners.
There was always class and influence divisiveness in the South, as in the rest of American society. It's just that the Southerners bridled more, being equalitarian, but were able to do less, because they were so very poor. That's why they formed organizations like the Klan, to try to offset the political power of the Reconstruction regime. But they were coopted and used from the git by the gentry -- well, it was founded by Forrest, and Wheeler -- so the Klan never could have become what its followers hoped, for better or worse. Particularly since it was a subterranean, underworld society suffused with vindictive violence, and always therefore subject (as the FBI discovered when vivisecting Satanist cults among West Coast kids) to leadership's being compromised and led from below by the most lurid and violent appetites. IMHO.