It looks as though Miami will be unaffected...
What are you looking at that leads you to think that? You are aware that the paths shown on news reports pertain to the eye of the hurricane, not the whole hurricane, aren't you?
I'm looking at a hurricane having a ~300 mile diameter, which is about twice width of FL. That the eye of the hurricane may miss Miami is absolutely no basis for thinking Miami "will be unaffected."
I'm hearing that Miami will suffer storm surge for sure. Parts of Miami flood in passing-through heavy rain. In my mind,
suffering storm surge is far from "unaffected."
Forecasted track and wind speeds at 6:00 p.m. today. (It's ~6:30 p.m. as I write this.)
Charleston, SC and points farther north on the Atlantic coast appear unlikely to suffer much beyond heavy rain, flooding, and high winds of the sort brought by a big thunderstorm.
In any case, my idea of "unaffected" is what London, England will experience as a result of Irma.