I'm not sure what you mean by "come out of the VIN pin for power" but if you plug 9V into the power jack you will get 8.3V out of Vin, which is what you put in less the 0.7V drop on the protection diode. However that power is not particularly useful. You still get 5V out of the pins on the board. And if you try to somehow shove the 8.3V into the LEDs you will then blow up your processor as the 8V feeds back through the processor.
You could conceivably put the 8V into a transistor and use the processor to turn the transistor on and off.
As for the chasing effect, if you put the pins in groups of two, or three, it would still look like a chaser, but only need half (or a third) of the pins.