It's a curious issue, between Choice and choice.
Bad Alias, you could well be right that the only real choices are between acting in accordance with one's true nature, and acting against it. A Choice.
On the other hand, the way Jim has spoken about it doesn't necessarily line up with that. What he has explicitly said is that for each mortal choice that is made, more universes inside a greater multiverse are created. 4
Philosophically you could argue that ALL Choices are choosing to act with or against one's nature, even if it is as mundane as which burger should I eat. But you could also argue that only during critical moments do we ever make real Choices, and everything else (the minor decisions) are all just ripples of the bigger Choice.
Curiously, the Many-Worlds Theory and others like it seem to agree that every option has an associated universe to go with it, based on probabilities. But of course as Stephen Hawking once remarked, all we are really calculating is the possibilities, not probabilities and we haven't actually measured any of these possible universes. He believed everyone had gotten carried away with the idea, and the truth was far more likely that there was only a very limited number of universes (maybe even only this one). The great thing about Hawking is he was smart enough to know how much he didn't know i.e. who was he to tell anyone what to believe?
From a purely logical point of view just based on WOJ, we can ascertain a few things.
1) Choice creates universes.
2) There is broadcast spectrum of universes in a greater multiverse (and their may be a greater multiverse above that - which Jim has hinted at but let's leave that out for the moment)
3) Therefore there have been enough mortal Choices (whether mundane or significant - acting with or against ones nature) to create an almost infinite number of universes.
This leaves some big questions.
1) What was the first universe? Was it Dresden's?
2) Before mortals were around to make Choices, and therefore more universes, how many universes were there?
3) Depending on how you look at history and what you believe, when did Harry's universe start creating more universes? Was this when mortals showed up? Is this what kicked the Old Ones out or locked them away? Is this what caused the War in Heaven and is the reason for Lucifer's argument with TWG?
4) If Angels and Old Ones existed before Time was a thing (as Jim puts it), before the all the universes then what were they all doing?(which is an oxymoron in itself - you can't exist "before" Time exactly...there would be motion if something existed and therefore Time would measure it. Although I suppose it could all just be happening at once and never fading as there might not be entropy, but what an awful existence that would be)
5) When (if you can even bother to ask such a question before Time exists) did TWG decide to start the party?
6) Does it even matter? In fact, there is a reasonable physics argument to say that because the Angels etc existed "before" Creation, the already have seen its end because from their perspective it would have simultaneously occurred along with Creation and all that's in between. This is why perspective is God. If you have all perspectives, you have omniscience (which is to say the same thing). In order to have that you would need to be omnipresent, and in turn that would make you omnipotent. So in a sense (as sort of confirmed by Uriel) TWG is constant, and everywhere. Which makes TWG everything. Kinda a scary notion, because like a single atom making up a person, every person and every single thing would just be one small part of the greater being that would be a Creator/TWG.
Sorry for the massive tangent. But we are getting into serious metaphysics and philosophical questions here.
Also - I think Jim was saying Harry had other options just in terms of the fact he wasn't sure which way he wanted Dresden to go (Hell aligned, Necromancer, Winter). Which I think is a bit unlikely, you can tell from how he writes Mab alone that he was always setting up Dresden to be on her team. It was always going to be Winter, somehow. Which isn't to say we might not see Necromancer Dresden or Lasciel-bonded Dresden, from parallel universes. In fact I wonder if we might see one of those in Mirror Mirror?