Board size definitely depends on what kind of water you want to expand your time on....flat v. waves. Also depends quite a bit on your weight and balance ability. Fanatic and Starboard both have a wid ...
The "os" stands for offshore; the model is forecasting for a point slightly further offshore so the winds are usually showing up higher over open water.
Not sure about the RRD, but I'm trying to find someone to let me demo a Fanatic Fly 9'6'' in the ocean (central FL area)...took one out on flat water and it seemed to handle really well.