Commas are used to indicate a pause. The meaning here is essentially the same, although lack of commas might indicate modification rather than coordination ("the short version of straight brown hair" rather than just "short and straight and brown hair").

Assuming the three adjectives are being used equally, (2) is a very unusual option. But if you mean to say "the short and straight kind of brown hair" that would be fine, with the lack of comma before the last adjective expressing a slightly different kind of relationship.

In the end, they all mean the same thing, but I'd suggest being consistent (commas or no commas) unless you intend a specific effect.

It actually looks very strange to me, unbalanced, like something (a second comma) is missing. In context it might make sense, with different emphasis on the adjectives, but I certainly wouldn't recommend that as the default pattern. It looks a bit like you made a longer expression (adding a third to an expression already with two adjectives) and then got a bit confused about punctuation, and added the comma to make it look less awkward without really thinking about the whole structure.

Certainly we can get a structure like that, maybe something like yelling, screaming small children where "yelling" and "screaming" are in a different relationship to "children" than "small" (they're the yelling and screaming kind of small children), but that's an exception, not the rule.

As a simple rule, most of the time a comma should be a substitute for "and", so try replacing it:
Yelling and screaming small children (OK)
short and straight brown hair (maybe OK, a little awkward)

Yes, I think I'd punctuate it that way. You're not wrong to think it might be a little awkward with many adjectives and no commas, but that's what I personally would prefer in this case. Note that comma usage does vary by different standards/individuals.

Yes, some people would probably tell you that looks more correct. But I agree that because there are multiple layers of commas, it looks confusing, so I would omit them. (In general I omit more commas than others, though, such as the 'Oxford comma'.)

In the end, this is a minor issue, compared to other problems in punctuation. But it's a tricky one to fully explain.