In space science fiction with races there are 3 races that usually appear regardless of number of races. Of how many races exists in the setting.
The Glamourous Race.
The most civilised and advanced of the races, their trademark is always very "rule of cool" designed space ship. Their advanced tech is based on the rule of cool. They can be equivalent to High Men
Their culture embodies wealth, culture and/or prosperity. Can't Argue with Elves
and Utopia Justifies the Means
usually apply , they can even be Space Elves
. They are the most likely to be extras and if they are chances are that they are pretty.
The Horror Race.
The least technologically advanced of the races. This is the race that is closest to Earthling 21th century tech level. If they are not members of the rooster, they are likely to be primitive and underestimated monstrous humanoids. They surprise the other races with having any sort of science fiction weapon or space ship. If they are humans other races may subject them to similar positive discrimination.
If they are sympathetically portrayed they are often victims to light cosmic horror. If they are not they are often horrible alien because Evil Is Ugly
or because the evil aliens needs to be defeatable.
Ancient Grome in Space.
The most space opera and political of the races. They are usually more technologically in the middle if they are not also one of the other races. Can be the Glamour race but usually is the contrast to the Glamour Race. Grome in space, is usually subject to civil war and crises. If the Glamour Race is the Deadly Decadent Court
, that is a good sign they are also Grome in space. Can be either The Federation
or The Empire
and <- Crystal Spires and Togas
The mundane race rebel against the political race or the political race are so civilised they are vulnerable
to attack from a brutal and horrible Gothic race. "Grome in Space" invade the homeworld of the mundane race.
A war in space can be become war of idealism versus realism.
A successful space opera is the balance of these tree roles even if they overlap or are overshadowed by a multitude of races. They can work like the space version of Elves versus Dwarves, They are the same race and the story with politicians in the background.
With no Glamour Race, you get extreme Dystopia. Without Grome in space, the other factions doesn't have a chance against The Glamour Race. Without Gothic race, the show is just to mind blowing and the audience have nothing to relate to.