Idon;t know much, but I think it was an early RTG system, like P96 or CGX, as you said. It only worked on a few cards (like P96 only worked with the Picasso cards initially) but unlike P96, was never really developed to support more cards. I think its most important feature was an AGA emulation.
VGR has a pretty good info page. I think the software's freely available, so you can try it if you have a supported card.