In my current campaign I have had a total of... 1 droid (an astromech), 1 Zabrak, 2 humans (both Corellian at that), 1 Devaronian, 1 Jawa, and soon to be 1 Ubese. With what talk I've had with my players, the current (likely) races I know about comes up to 1 Zeltron (a grown up version of a child NPC the current party is protecting), 1 Wookiee, and 1 human Mandalorian.

As for how they play them, the Zabrak is big and strong, the Devaronian shady but pretty much the face of the group, the Jawa is basically a druggie without the drugs, the droid is both cowardly and protective of the party. Ubese hasn't played yet, but from what I got so far, they're a strong silent, often-quick-to-murder, type, with a huge emphasis on the silent part. So I'd agree that, yea, alot of the alien races have their personalities based off the stereotype, but then again, alot of characters do (or are total opposites)

If, for a moment, we include near-humans who are almost indistinguishably human save for a creative skin color, then pretty dang common. Humans with head-thingies? Notably less common. Beings that don't even come remotely close to humans? Never seen one.

Our first group started with 2 humans and 2 aliens (a Twi'lek and a Selonian), but the Twi'lek player swapped to a Corellian after the first session (we just did a retcon that they were always human), and the Selonian player got tired of her character completely after awhile and sacrificed her character by jumping on a grenade so that she could play a Force-sensitive human. (Cleaning up all that fur was awful.) From that point on it was an all-human crew.

Then that campaign went on hiatus and when we started it again, two of the original players were replaced by new people who opted to make a Chiss and another Selonian (people like ferrets I guess) so we were back to 50% alien again.

We recently started a brand new campaign, and this time we have 2 humans, a Zygerrian (not an official race from the books but the GM allowed the player to use some stats from a Reddit post, I believe it was this one ) and I'm playing a droid. So 50% human again.

Our current campaign has one Twi'lek, one Bothan and one Wookiee. Two of us has back up character concepts, and both are non humans, one droid and one gand. So 100% non-humans.

I have nothing against playing a human, if the GM had a good reason for wanting all or a few players playing human characters I'd have no problem with playing a human. But given the choice I'll probably always create non-humans in any Star Wars game I play in, and I'll probably never re-play a species I have already played if I can help it.

In our ones, we had the most "common" species like wookies, twi'leks, mon cal, droids and similar, but the weirdest ones were a kushiban and a tchuk-tai XD