The building codes for South Walton County are on par with most south east coastal regions. Since mid 2000 they have been upgraded frequently and are listed on the county website. The specific enclaves (Rosemary, Alys, Watercolor...) usually have additional requirements and a list of approved builders that they will not deviate from. This is both good and bad in regards to permitting, subs, commodities...
The town of Prominence is a good place that's newer. I think it's a DR Horton development which off the So30A is not common until post 2007. It has the HUB with good amenities for families along with Deer Lake Park (I think) nearby. Watersound is estheticly nice with a good beach club for owner/guests. Watersound will cost more (usually) but on So30A this is the deciding factor in purchasing VRs, second homes,... Out realtor is Jonathan Spears (Sotheby's) and he can help as you get closer with the proscess. This would include just general info with no solicitation.
As property management go we have used 360 Blue the past four years but as with any there are pros and cons. The PMs will influence your profitability more than most think. There are PMs specific to regions as well as some being approved for the developments (St Joes,...)
The majority of destruction being shown in Mexico Beach is via old homes with lower building code from decades ago. Mexico Beach has height requirements and thus condo developers stayed away and concentrated in PCB. This is why there is variation in the same strip of the Emerald coast among prices, patrons,...
I could talk for hours on this subject so let me know if there are other questions. I've been visiting the region for approx 30 years and investing for approx 10 years. I have seen both the boom and bust of the emeral coast.