On working with an agent

Having made it over a major hurdle on the track to getting your work published, I thought I’d send a secret communication out to let people know what it’s like working on your book with an agent.
That was the idea, anyway — problem is, I’m not sure that I have that much to tell.
Yes, I’m working with my agent on my book, but I’m starting to get the sneaking suspicion…
… wait for it …
I’m starting to think they all do things differently.
Now, the (wonderful) person I’m working with does a lot of the sorts of things that I had compartmentalized as “editor stuff.” Some of her feedback is along the ‘agenty’ lines of “the scene on page 8 feels kind of off” or “would Joe really ask her that?”, but just as many of her notes are detail-things like “you’re missing a ‘the’ on page 48” and “you switch to the wrong verb tense in the scene with the giant chicken.”
Now, I might begin to believe that I’d simply misunderstood what it is that an agent does for their author — I’m a tyro in many things literary; it wouldn’t be that big of a surprise — except for the fact that I work around (if not with) another agent, and her approach involves feedback like:
“What if the main character were japanese instead of romanian?” or…
“What if they were in high school instead of the CIA?”
Big picture stuff, if you see what I mean. Agenty-stuff.
I’m told that another agent I know doesn’t do either of those things, and approaches her job as something between a therapist and a legal representative the mentally unfit.
Are any of them wrong? Are any of them, in some strange way, not agents?
I don’t know. I don’t know if I ever will. I’m glad I found the one I did, and I think that will have to be enough.