So the PR person forwarded my request to Bacardi Brand Master (and production nerd) David Cid, who outlined the basic differences below.
Superior and Carta Blanca (aka regular Bacardi) are one and the same. A blend of rums aged a minimum of 12 months. Dry and balanced. Meant to neither dominate nor disappear in a cocktail.
Heritage/1909 is a tribute blend of Bacardi Superior at the proof you would have found it during the golden era of rum cocktails, 44.5% abv (89 proof). Same production approach as Superior, with higher proof, which in turn carries a slightly different intensity to certain notes. Meant for use in classic rums cocktails, like the hand-shaken daiquiri.
Maestro Gran Reserva is categorized as part of the Gran Reserva line along with Bacardi 8. It is a double aged rum bottled at 40% ABV. Mellowed for one year in American white oak, blended, and placed into aging again for another 3 months. A more robust nose and body, meant to stand out in a cocktail.
NEO, part of the FACUNDO Rum Collection, is a blend of medium-to heavy-bodied rums aged up to 8 years. Once the aging process is complete, the rums are filtered to allow for a hint of color, and a significant amount of aroma and flavor. Offering an oaky aroma with hints of almond and floral notes, with a clean, balanced finish, NEO is made for sipping on the rocks.
Cid also notes: All these rums are aged in American White Oak. All Rums go through charcoal filtration; some more than others.
It would be interesting to taste all the rums together sometime, alone and in cocktails.