I've ridden from Destin to Panama City along 98, the beach road (old 98 but not designated that way anymore), the bike paths, and bike lanes where available. The worst of the area is through SanDestin, as there are no bike lanes and no shoulders. I've gotten up onto and ridden on the sidewalk through this area. It can be hairy when busy in this stretch. There are bike lanes along a fair amount of 98 through the Destin area, though.
The 30-A separate bike path is 14 miles long, and extends from the intersections of 30-A with 98 at both ends (Santa Rosa Beach at the west end and Inlet Beach just past Alys Beach/Rosemary at the eastern end.) The bike path is OK for medium speed cycling, but if you're going 20+ you come up too fast on people coming in and out of driveways. I use the path in the more isolated areas, but ride the roads in the condo stretches.
Going past the Inlet Beach terminus into Panama City across the 98 bridge looks worse than it really is. I've never felt any traffic pressure while crossing.
Also check out the Emerald Coast Cycling Club. I've ridden several of their "off-the'beach" rides and enjoyed them.