Got some time to tinker with it again and here is what I found thus far. If I plug all in, the Amiga 500 doesn't seem to boot where the floppy drive makes the usual sound.
If I unplug the VGA adapter cable from the GBS 8200, the Amiga boots. I can then plug the VGA adapter on the GBS 8200 but still no signal. However, if I switch the display settings between 640x480 & 800x600 the Workbench 1.3 insert disk hand flickers on the screen with a purple background and then it goes to "No Signal". See images.
The RGB<>VGA Adapter is wired as follows:
