A cambered bar is a long bar with a 4 inch dent or “camber” in the middle which makes it possible to increase your range of motion by alowing you to lower the bar past what is normally “chest level.”
A seated half press in a power rack is actually a triceps movement. It starts higher than a standard overhead shoulder press and emphasizes the part of that movement where the triceps take over.
As for the A1/A2 designations. You move back and forth, but do no superset. Casually alternate between movements and rest for a bit. I tend to keep rest periods short, though.
Unless you are prepping for a contest, I’d rather see you go with the approach that I outlined in the thread “5x5 routine” started by DA MAN.
Joel
P.S. While I did not recommend the seated 1/2 press in the above thread, if you ever want to do it, check out Poliquins Tricep article in issue 61 for a description.