Nice write up. I concur with what you wrote, especially the barrenness of FL-20 but will add a few points about US 98.
To me, the US-98
corridor is pretty good overall. There are numerous county and/or city roads which take you off of 98 and its traffic. Of course, due to being on or near the coast, 98 has a LOT more services available and, to me, is greatly more scenic that US-90. As long as the services are not closed due to a hurricane wiping everything out for 50 miles or more
. Plus the stretch between Navarre Beach and Pensacola is just sublime, one of my favorite. Not much traffic and literally 150' from the white sandy beach at times. However, I have ridden this stretch 3 times and every time had strong winds from the east. I don't know if this is common or what but it should be noted.
IF you are headed toward/from the south, say Key West I don't know how much extra miles are needed. It may be the pretty close.
To me, the big negative of US98 is the 11-mile stretch on US-98 between Navarre and the west side of Mary Ester which has ungodly traffic volumes of 40k+ a day. Granted there is a 2-3' shoulder with 2 lanes of traffic in each direction so it is doable. Just fairly stressful. All of the 4 riders I rode this stretch with said they would do it again as they really wanted to ride along the coast instead of 90.
Also, there is the (hopefully temporary) closure of the bridge over the Pearl River near White Kitchen, LA, that got destroyed in a hurricane recently. That closure really adds some miles to detour around it if you want to go to New Orleans and continue along the Gold Coast to South Padre Island, TX.
Again, thanks for the write up. I bet some people will not do it FL-20 if they read your post.
Tailwinds, John