What genre would the "Choose your own story" mobile games fall under?

Solution 1:

I would say those games fall under the category of Visual Novels.

The Wikipedia article is actually quite interesting, because there's a paragraph about Visual Novel elements in an RPG.

Overall, I would say that Choices and Episode are just Visual Novels, but something like Kai Chronicles is a Visual Novel with RPG elements, as it fits your description (Inventory, Weapon slots, Stats, etc.).

Solution 2:

Episodic Visual Novels in their gameplay.

Now, one thing to note is that video game genres are not strict "one or another", more like a wibbly-wobbly mess of terms. The games you referred to are mostly Visual Novels, but also contain some elements of RPGs, but they lack what one would traditionally consider RPG gameplay, that is to say free form action. Instead, much like in Visual Novels, you read events until you arrive at a "story junction" and select a path (option) to progress down to.