I doubt very seriously a 'leftover' ACC would have all those schools. Neither the SEC nor BT act that pint will want to leave behind the possibility of new TV viewers or potentially top programs.
The state of VA is massive important, and UVA is AAU. Anybody who thinks UNC would go anywwhrer without UVA is out of the loop. The SEC may not want to have total control of VA, but if the BT takes UVA, the SEC will then take VT as a blocking move. Likewise, if the BT takes UNC, the SEC will take NCSU.
The SEC has no need of GT, but AAU GT has perfect location for BT football getting into the South. And AAU Miami clearly could add a good deal to BT football.
If the ACC loses those schools, the Big 12, pushed by WVU and Cincy, will focus first on getting Pitt.