This is going to very a lot from field to field. Some fields try to have extremely sophisticated order of authorship rules while others do not. For example, in pure math there's pretty much no emphasis on author contribution order. In contrast, astronomy and biology often have first, second and third author at least, and sometimes later authors listed alphabetically (until one gets to the very last author who may be someone who runs the lab but didn't do much directly).
In your hypothetical, all of them will list it on their CVs. They can signal to people that they did more in part by giving talks about the research or mentioning explicitly what they did in research statements or the like. But that will often be a more natural thing to talk about in interview contexts.
And regardless of field, regardless of how much Smith contributed, it will definitely help Smith in terms of graduate school. How much so will depend on the field. For example, I have a friend who is in astronomy. As an undergrad he was on a paper with about 40 authors. They listed five people in order and then listed the remaining alphabetically. My friend was listed third. I strongly suspect that when he applied to graduate school, they noticed exactly where he was on that list. But even if he had been listed in the long alphabetical section, it would still have helped.
