I thought i was not using it but conceded that possibly I was and had not realized. So I turned it off. Now, nearly two weeks later nothing has changed in my daily iPad activities. So, it will stay off.
If you're using the first two, then you're using features that have long been supported by machine learning. But I think "Apple Intelligence" refers to the particular set of features enabled by its particular set of on-device (or "Private Cloud Compute") models – that is, those downloaded and readied when turning on the feature in Settings.