144 BCD is the most common for track cranks. The Vuelta Pista has a reputation for being very low end. As for using the double chainring on a fixed gear, you might look here to see how this may or may not work.

SRAM S300 is a track crankset which means it only has one chainring.

You didn't get any responses because of a combination of tl;dr + you didn't seem to have done enough research on your own yet.