from the firestore doc

In some cases, it can be useful to create a document reference with an auto-generated ID, then use the reference later. For this use case, you can call doc().

import { collection, doc, setDoc } from "firebase/firestore"; 

// Add a new document with a generated id
const newCityRef = doc(collection(db, "cities"));

// later...
await setDoc(newCityRef, data);

Behind the scenes, .add(...) and .doc().set(...) are completely equivalent, so you can use whichever is more convenient.

my question is that does const newCityRef = doc(collection(db, "cities")); count as 'read' or 'write' without using setDoc(newCityRef, data)?

Let's say if I generate 100 document references but don't save them at all, my 'read' or 'write' count is 0 or 100?