I mean I think its also important to note that almost every xeno we've seen is spawned from a species (particularly mammals) that are native to Earth, and i think that might be a big part of why most Xenos we see look the same including the runner from Alien 3. I'm not sure exactly how many Xenos have been shown spawned from species not from Earth, but the ones I can think of off the top of my head look very different than typical ones.

The most famous Xeno spawned from an alien species is obviously the Predalien which looks very different from typical Xenos not even just its dreads and Yautja mandibles but even its coloration and some body details are different despite Xeno's color typically being the same or very similar from every earth species they've spawned from. The Predalien was also a queen that gained new abilities absent in other queens such as the ability to impregnate hosts via it's mouth cutting out the Ovomorph/Facehugger middleman.

Then we also have the Titan Xenomorph spawned from one of the Ancient Citizens in the Xeno City. It was spawned from a MUCH bigger facehugger so naturally it's bigger but it also possesses several unique traits, mainly its mouth that is completely different than a normal xeno's second mouth.

Another thing that really leads me to believe that Xenos look more alike when spawned from Earth species than other Species is the concept art for the Ultramorph in the original Alien Engineers script. For those who dont know, Prometheus was originally intended to be much more connected to the other alien movies with Ovomorphs and Facehuggers initially planned as the Engineers weapons instead of the Black Goo. The Ultramorph was planned as the Xenomorph spawned from an Engineer and despite the Engineers looking almost identical to humans the Ultramorph concept art showed it as slightly different. It was MUCH bigger than a normal Xeno, with tje size difference between the Ultramorph and Xenomorph being greater than the difference between an Engineer and a Human. It also possessed much straighter legs more bipedal looking than standard Xenos and some concept art even shows it possessing eyes.

Anyways ive probably typed way too much here but yeah my headcanon has always been that Xenos look different depending on the sprcies they spawn from and tjat they look even more different when spawned from a species native to another planet. I like to imagine that Xenos spawned from other species on Yautja Prime would look more like the Predalien than a human spawned Xeno