How do you decide how many scenes should be in a chapter?

Depends. I've seen chapters that are a sentence, and that's it. Sometimes, the white space that surrounds that single sentence can give it impact that it might not away have.

It's a stylistic thing. Just do what feels right. And I personally wouldn't strive to be too different too much, or without a clear intention in mind (ie, I am deviating from what I would normally do because of *this*), otherwise what is different just becomes gimmicky.