Today starts the mid-major portion of the series, where the existing conferences (and their predecessors) often had little to tie them together in the first place beyond rough geography (and sometimes not even that). So the post-16pocalype alignments are based more on location than anything else.
When the super-conference structure fell apart, the major conferences (which had been BCS AQ conferences once, or at least had been part of the Bowl Alliance) tried to align mostly based on traditional rivalries, but the non-AQ conferences mostly lacked those. So the new non-AQ conferences were built up largely along geographic lines, though with some eccentricities. In the rush to 16-team super-conferences, Conference USA had picked the last two Florida schools and the schools left behind as the major conferences picked apart the Big East. The southeastern schools from the CUSA of the super-conference era became the heart of the new Gulf Coast Conference.
League Name: Covering only four states, all in the same region, Conference USA didn't seem like an appropriate name for the new conference. The Gulf Coast Conference was apparently the name of a short-lived conference in Texas once, but no one had used it in decades, and it seemed like a good fit.
Members: All the remaining Florida and Alabama schools (save Miami), as well as Southern Miss and Tulane. So Central Florida, South Florida, Florida Atlantic, Florida International, Alabama-Birmingham, Troy, Southern Mississippi and Tulane make up the conference.
Advantages: The simmering feud that is the USF-UCF rivalry. A bit of history with Southern Miss-Tulane. Schools in recruit-rich Florida and Louisiana. Two of the largest schools (and strongest minor conference programs) in the country in UCF and USF.
Disadvantages: Every school in the conference is a distant second (at best) in prestige to other schools in its state (and FAU and FIU are well behind their conference mates USF and UCF). Its strongest programs are likely desperate to leave for a higher-tier conference, though the end of conference championship games and 12-team (or larger) conferences limits opportunities.
Summary: As mid-majors go, this is a pretty decent conference, with one formerly AQ conference team in USF, another that is currently regarded as a leading candidate to join an AQ conference (UCF), and another program that his had some high-profile history (Southern Miss).