I prefer to negative split and get a much better experience. I have seen examples when running with mates that I need longer time gain speed and prefer longer intervals.
Do you think the best way to guess whether you are slow or fasttwitch is by looking at what your preferred starting speed is? For instance, some like to start off really hard, does this mean they are more fast twitch? I could use the metaphor gasoline and diesel here, obviously diesel being slow twitch.