To be honest, I haven't heard any of Univer Zero's 90s and 2000s material, but I have heard the ones you listed and Uzed and Heatwave, both of which are great, more relentless, and darker, if possible. According to reviews I've read though, their latest material seems to be consistent in quality. And yeah admittedly, I haven't a clue of what defines RIO. Magma seems to fall into the Zheul category, although some claim they really play RIO, while still others say their music IS zheul combined with progressive rock and other elements which make it zheul, like you said.