Hello, and welcome to the forum!
If you like the existing ChoiceScript games, then I think that would be a good option. They are popular, they have a consistent style, people know how to play them, they have well-established distribution channels, and it’s easy to get started in ChoiceScript.
I don’t actually know how much you can customize the style and the mechanics, but that may not be necessary for your story.
About publishing a Twine game as an app: In principle, you can build a hybrid web-app with tools like Cordova or Capacitor. But it also depends on the store… as far as I know, Apple does not really permit such apps, while Google changed its policy sometime ago and allows them now. (Don’t know if that’s the status quo.)
For Unity, definitely check out ink: ink - inkle's narrative scripting language, Ink Unity Integration | Integration | Unity Asset Store.
Regarding itch.io, I think it’s hard to build a fanbase, simply because of the huge number of games. But of course, it can’t hurt to put the game on there, if you don’t have an exclusive licensing deal with another platform. And it would be good to observe the usual rules of marketing: have an attractive cover image and a good-looking presentation page, use the correct genre tags, and potentially build a network by leaving comments and feedback on other game pages (without spam-marketing your game, ideally).
On the Choice of Games forum (and here), there’s the advantage that you have an audience who is already interested in the type of game you’re going to make.