Ah. I take it you're a psychiatrist or other medical professional? And your basic view is: humans are a species. They are a certain set of organs and personality traits and so on, with diseases and variation therein. But basically, one set of creatures, with whom you are thoroughly conversant and don't have more questions to explore. Fair enough.
I'm in grad school to be a psychology professor. Which means that in addition to teaching, you also have to do research studies on human behavior. I'm up to my neck in what people are capable of cognitively, emotionally, etc.
But being aware of what we are capable of makes me aware of what we are
limited to. Pushing past those limits, thus, is a fun creative exercise for world building and characters and such.
I come at it from a different place. I studied humans as my specialty too. But I studied history and political science -- SOCIETIES, not individuals -- and saw there's incredible variation over time and space in what human societies are like.
My focus is on Social psychology, which deals with all the stuff relating to human interaction (it also now has Evolutionary psychology in there). So, thinking about this sort of stuff - what makes people tick - is part and parcel of what I
will be doing for the rest of my life. So, when I get my spare time, I'd like to apply those questions to things that don't exist, things that I know people
aren't, and ask the same kinds of questions I do about people.
For instance. Warforged and Shardminds don't need to breathe, sleep, or eat. This is fairly huge. It means that they can
do a lot of things that organics can't. And they're not vulnerable to the same things. A group might cultivate a chemical weapon (or other sort of inhaled irritant) and fill their "base" with it, rendering it fairly problematic for organics to invade. Or they might construct an underwater hideout, raiding coastal areas and having no problems in or out of the water. They could serve as wreckage crews - retrieving the cargo of lost vessels. They are great miners, not susceptible to poisonous gasses (the reason miners used canaries), not needing to worry about blacklung or other unfortunate effects. They can work all night, and do not "need" breaks in terms of biological needs. They make better eunuchs than eunuchs. They can sit for LONG periods of time, inactive, so a PC could be introduced simply by being unearthed from a ruin.
But just because they DON'T NEED TO, what does that mean for them? Might they like to? For example, drinking water to clean their throat or to enjoy the temperature. Drinking things we can't because they appreciate the texture or the "flavor". Their senses of touch and taste and smell might be dull, so they seek out even sharper, harsher things just to be detected ("Oh god the Warforged hugged a skunk!" "I wished to smell something.") Would they be non-plussed by biological waste, or disgusted by
all biological compounds (seeing no difference between blood and urine). If they aren't capable of sex, then what do they do to express companionship? If they don't have a drive to procreate, do they have another drive to make more of themselves, expressed a different way?
And just because they are not vulnerable to some things, it means they are vulnerable to new things. One lost at sea would be lost at the bottom of the ocean, unable to find his way home. A cave in means they are trapped, perhaps forever, entombed. A warforged who is not "dead", but just "taking 10 on his death saves" might be believed dead and wind up as scrap metal/spare parts. These are phobias that, while similar, are a little different.
Shardminds are telepathic. So how is this going to effect their body language? And on the topic of body language, the faceplate of the warforged is fairly hard, which I think would limit facial expressions. So how do they communicate nonverbally? Would both of these races simply not pick up, or just not understand, the flailings and twitchings of other races (the same way other races just have trouble reading them)? An empathically "tone deaf" shardmind/warforged sounds like a really fun character; a "tone deaf" human would garner rolled eyes and he'd be considered a loser or a jerk, but if the
race has this trait, it becomes a characterization about them as a people, it effects their relations with others, it goes beyond "That guy is a bit underdeveloped" and becomes "OK guys, remember to express yourselves fully and be blunt when talking to these guys".
And don't even get me started on tri keen. I grin just at the IDEA of making clicky mantis noises (along with doing mandible motions with my fingers), perching very close to sleeping companions, and otherwise just being
unnerving. And being utterly terrified of females.
This is just more fun to think about then being limited to just culture/religion/ideology that humans provide. Don't get me wrong. I love anthropology, sociology, world religion and politics and all that good stuff. But I've been exploring and observing those for a Long time, been saturated with Tolkein and typical fantasy for about ten years now. Looking beyond to "how would everything be different if I had six arms or didn't have any biological functions" become more intriguing.
Simple philosophical questions like "What is it to be human" and such like that become far more when you've got lots of not-humans. But then, I also think
transhumanism is intriguing.