As for the forward speed question, generally when you have such a fast forward speed, the features that are steering the storms are pretty well established. It's not necessarily that there is little spread because of the fast forward speed; it's that there is little spread because of the persistence and intensity of the weather features that are causing that fast forward speed.

If the storm were moving slower, there could be the same spread or there could be more spread. It all depends on what the models are seeing as the factors that will influence the track. The storm would cover a smaller area of ocean in the same amount of time as if it were moving at 20+ mph, making that spread a bit smaller, but it could also be nearing the edge of a subtropical ridge, where track forecasts become a bit trickier.

Simply put, I'd say it's not the fast forward speed that results in those differences, but it can be used as a proxy to try to understand why differences in model spread may exist.