Any question answered...

Won't the rear wheel's position depend on the gear you're running?

If you're a proper aero-weenie, you find the optimal wheel position then magic gear to get the ratio you want with the wheel position you need.

1R8 is the Tester recommended racing chain, 1Z1 is for training

1Z1 will be fine for track racing, the 1R8 is just more tarty but less corrosion resistant and more expensive. Because the 1R8 is a lot stiffer, I'd expect it to be a bit more efficient at high chain tension because the roller should land on the tooth more precisely, but we're talking very small fractions of the total power loss, and that total is only about 1.5% of input power for a clean and properly lubricated chain at typical cycling power and drivetrain configuration.