I don't believe Balloon framing was the most popular form of construction in the antebellum period. While there is some evidence of it's use prior to the war period, it didn't really become popular until a bit later. It was most popular from 1880-1930. The fire hazard is from the exterior wall studs going from the foundation, all the way to the attic. The flooring levels in between, are "notched" into the walls, leaving a free flowing air duct the length of the entire wall. A fire could quickly go from first floor to attic. I've worked on plenty of 19th century homes, & have seen balloon framing. However, I haven't seen it on the antebellum houses, I've been on.
The typical roof construction (antebellum) has what we call today, slats, or spaced sheathing. They weren't using plywood. They had boards spanning horizontally across the roof rafters. These boards were spaced anywhere from 1 - 3" apart. Then the wood shingles were installed on top of this surface. The gap between the boards was genius for longevity. The purpose was adequate ventilation, which equals rapid drying of the shingles. Properly installed, wood shingles absorb water, & expand, creating a water proof surface. It is/was not uncommon to look up from inside a wood shingled structure & see daylight. However, once wet, they swell, & seal. The need for great ventilation is somewhat obvious as, if they stay wet all the time, they'll rot out prematurely.
This spaced sheeting, wood shingle design is one of the better roof designs for longevity, & was in use well into the 20th century. I've been in structures that had this design with the original wood shingles that were 50+ yrs old, & still functioning. We don't build them like this anymore, & therefore wood shingles don't last nearly as long today. That design was great for roofing performance yet, terrible for fire prevention. If fire hit the roof, forget about it. It's over. Many local building codes, & insurance companies today, forbid the installation of wood shingles.
I've been a Contractor for nearly 30 yrs. I specialize in roofing, I'm also a carpenter. Just sharing a little bit that I know on the subject.