OK, I've just got back into playing FFX-2 and will probably take a while to
finish it, but I have a few questions about the alternate endings and other
things.

Is it a whole long sequence of things that determine an alternate ending or
just one last scene? I don't mean things leading up to it, but what makes
the end different. Is it different final scenes after a presumably final
battle?

Is it true that you can easily replay story mode with all stats and items
reloaded from your previous game to make it a relatively quick and easy
replay?

That's about all the questions for now.