@BangoSkank I'll try to cover everything you're asking about, but my answers for some of these are going to be a bit vague.
In general the galaxy is populated by a very diverse variety of intelligent aliens; very Star Wars like, but humans (and a few others) are more common than most. A long, long history of galactic war has reduced most of these aliens to slowly-dwindling vagrant populations after the destruction of their respective homeworlds.
Humans (also called Terrans) are among these space-drifters, but are unique in that their population has
increased following the destruction of Earth, rather than gradually gone extinct. Theoretically this is due to a human predisposition toward adaptability. Humans are more resistant than usual to spaceborne radiation sickness, and are also remarkably compatible with cybernetic and genetic augmentation. As a result, Terrans are very diverse even among their own species. "Halflings" or "Dwarves" would potentially fall within gene-augmented Terran populations. Terrans are generally stereotyped as being like space-roaches: ubiquitous and impossible to exterminate.
Cybernetic augmentation is common enough, if you can afford it. This includes full-body prosthesis, and potentially even full cybernetic conversion. Though at that point you are no longer considered your original species, and are instead a SINTH. Terran-converted SINTH are among the first to exist, and the most common, and are regarded as a far more civilized successor species to humanity. True AI is rare and usually created/discovered by accident, though there a few fully-cybernetic species in the galaxy, nearly all of whom are allied with the high-tech Arc Luminous.
FTL has come in a variety of forms in galactic history, though most have become obsolete due to resource exhaustion. Currently it comes in two forms: Ether Drives, and Hyper-Ring travel. Ether Drives use special Ether fuel to create a special pocket of hyperspace around a ship, allowing it to travel faster than light. It's fairly zippy, you could cross the entire galaxy in about eight years this way (assuming you had enough fuel), but the fuel is not cheap, so it wouldn't be the most economical. Hyper-Rings are massive portals directly into hyperspace, allowing near-instantaneous travel from ring to ring. These are tightly controlled by the Spacer Commerce League, who are the only ones that know how to activate, run, and repair the rings. Most Hyper-Rings are mobile, able to be towed around the galaxy via Ether drive, but a few Mega-Rings are immobile transport hubs.
In terms of playable characters, humans are generally considered the default, but I'm open to nearly anything. There are a few species of noteworthy aliens in the galaxy, such as the Lsola (plant folk) and Tora-Tora (catgirls) as well as the SINTH that I mentioned earlier. Basically float me an idea and we'll see if we can make it work.