Image from Arik
Superiors, or su for short, are humans who have augmented their biological nature through germline-engineering and bodymods, making them more powerful than baseline or nearbaseline humans in multiple ways. Other biont clades may have comparable abilities, and may also be referred to as superiors, but usually with some qualifier indicating their origin; "superior" without any qualifier refers to a human. Many superiors are superbrights, or have astonishing creative or athletic abilities. There are thousands of clades, species, phyles, races, and variants, but they are not as diverse as the tweaks. They tend not to be interested in reproduction to the extent of those phyles under them, preferring to explore their own rich potentials (there are a few exceptions though; House Stevens comes to mind). Some, such as the empath phyle, have had a huge influence on Terragen history and politics. Others, such as the large and important House/Suclade of the Genen, sometimes incorporate "tweak" elements but are still regarded overall as su.
Some nearbaseline and other non-su humans are able to augment their genotype with so much su genome that they become true su, although becoming su is much harder than becoming cyb or becoming pseudo-superior. Many su eventually become Po or Uploads when they weary of embodied human existence. Perhaps three or four hundred trillion sophonts of the galaxy are su.
Image from Bernd Helfert