Nightkin

So super mutants are very bulky and looks huge just like their counterpart nightkin, but are they just always bulky in general??, because there is no super mutants nor nightkin that are skinny, Slim and even obese, just that they are always bulky

As stated in the DLC Far Harbor Vim affects Super Mutants sanity. As of now only Ericson show this effect. So is this effect also possible for a Nightkin? Or are they way to insane so that they are unaffected?