Guns

There will be a focus on four kinds of personal firearms in the setting: Projectile, Laser, Plasma and Sonic.

Sonic weapons have replaced tazers for the most part, and are very popular in ship-to-ship boarding actions, as there is no risk of penetrating the hull and sonics ignore body armor that isn't heavily sound-proofed (and even then the vibrations will rattle your skull a bit). They're the non-lethal main, basically.

Lasers are, for the most part, in the form of tools modified into weapons or sniper/hunting rifles, since in normal combat being able to see where you're shooting is kind of important, and because they're liable to scatter and disperse in the kind of dust and smoke you get in large-scale combat. It's often used by assassins, but also by hunters. Lasers generally sound like loud pops or cracks followed by faint buzzing, with the more powerful types of beam-weapons being as loud as conventional firearms in our modern world.

Plasma weaponry serves much the purpose of lasers in most space opera, the bolts of superheated plasma you fire are slow enough to be visible and look awesome, and most plasma weapons are indeed called "blasters". Plasma weapons have recoil and can overheat the barrel, and yes, they do make 'pew, pew'-sounds. Oh yeah, you get green, white, blue, red bolts. Depends on the gas used.

Projectile weapons mainly come in three varieties, flechette, caseless chemical propellant and electromagnetic coil-weapons. Flechette weapons are often used for those wanting something with punch that incapacitates rather than kills, most police forces around the galaxy uses some variety of them, with everything from tranq-darts to versions of smart-bullet beanbag ammo that knocks out but leaves no lasting injuries. Most flechette weapons use compressed air or other gases to propel the ammunition, and it's not 100% safe, you still get occasional fatalities. Still, as most humans say, better to have trigger-happy law-enforcement agencies 78% less likely to be able to kill you than what we used to have.
Caseless is basically regular firearms, but without shell casings, the issues had with such weapons having been solved at this point. Caseless ammo basically has cartridges where the body is the propellant itself, and the bullet is directly fastened to it, this allows for smaller cartridges and no flying shell casings. These guns still have to eject the burning gases and particles, so they still need about the same amount of moving parts, but at least the load of a pistol is bigger, and calibers can be larger. Firearms with caseless, chemically propelled ammunition are extremely common, but for understandable reasons they're rarely used in spaceships or on environments in space.
Electromagnetic coil-weapons are heavy-duty stuff, the equivalent of a Desert Eagle .50 but more accurate and a hell of a lot deadlier. Ironically, the projectiles are much smaller. Attempts at making larger coil-guns than pistols have yielded varying results, for the most part the weapons require wielders who can handle the recoil, which means either people in military-grade powered armor or species much stronger than humans.

The Veen - setting-building notes

I have a very specific thing in mind when I write the Veen. It's the early Victorian British, mainly, the early to mid-1800's, but with fashions and art more suited to the Rococo or even Renaissance, lots of gaudy colors, and even their battlecruisers have useless crenelations and coral-like protrusions. The mentality is very much White Man's Burden, arrogant Imperialists who believe just because they have the biggest and most powerful stuff they deserve the largest pieces of the cake, and anyone not as advanced as they are inferior and deserve barely mockery.

Note that these are technically good guys. Yeah.

In the setting, the Veen loathe/hate/dislike humans for two reasons. The first is the same reason they dislike any species not their own: They're not Veen. Veen society is, for the most part, deeply bigoted towards non-Veen.
But the second reason, the reason why bigotry towards humans is actually encouraged by the governments of the Veen, is known only to a few of them. It's a deep, dark secret, and one they would prefer never to get out: Humans and Veen might be related.

Genetic deep scans reveal human and Veen to have more than 99% of their DNA in common. In fact, the scientists who performed the tests surmised it would not be impossible for Veen and humans to procreate.

Add to this that humans smell good to the Veen. Their olfactory senses are slightly sharper than ours, and to them, our natural body odors, even hidden away by washing and use of perfumed hygiene articles, trigger several bodily reactions, such as endorphins and other natural reactions. Basically, they like our smell. Some Veen have surmised that this is somehow intentional, going by the Precursor Theories that are common in the Alliance (the idea that a precursor species went about the galaxy seeding life and technology) and theorizing that humans and Veen were made for one another.

...naturally, a fairly tightly wound, up-tight monoculture like that of the Veen Empire can't very well have a walking aphrodisiac species gallivanting about in Alliance space.

For GM's this isn't all that difficult to portray. Humans get a slight bonus to social rolls against Veen, and that's about it.

As for what Veen look like, well, they look mostly human-like, but instead of scalp-hair they have thick, vestigial, mostly useless tentacles, and instead of eyebrows they have little neat fleshy ridges. They have eye-lashes, but that's just evolutionary good sense. The tentacles are pretty much just dead weight, and men have shorter tentacles than women (they still reach the shoulders by adulthood, so there's very little difference to non-Veen). They're also vaguely erogenous zones, about as sensitive as ear-lobes. They're slightly shorter on average than humans, and their eyes lack whites and pupils, tending towards solid-color hues of green, blue, black and purple. They don't see much better than humans, though.