I've sent you this directly as requested, but for the forum:
1. Can you reproduce this behavior w/ a single device? I.E., just the joystick?
Yes, multiple times each with joystick, with throttle and with the pedals. Each test was done with a single device and was plugged in before booting up the iMac. Same with all three devices connected.
2. When are you unplugging the devices? After you have already started X-Plane? Then you also plug them back in while it is still running and they work then?
Yes, XP is running and then no input device is working, then I unplug the devices (single/multiple) and plug them in again and I have to calibrate, but all devices are working after they plugged in. Interesting is that in the devices menu of xp you see grey line with the proposed axes (plural of axis?), but the axis do not show red or green. In some cases they arent shown. That will be restored by plug out/in again. The appear then.
Same behaviour as mentioned in comment from DrBen (above). I see the same values and amperes in system report.