Q: iCloud setup with one Apple ID and multiple devices

Yes.

You can't. Each device would need a separate Apple ID, hence, a separate user account.

You can attach multiple devices to a single Apple ID. But for each user to have their own separate cloud account they would need a separate Apple ID. So perhaps you are not explaining your questions adequately.

Is it possible you mean the same iTunes account?

What, exactly, are you trying to do? You can use the same iCloud account on as many devices as you want, as long as you don't turn on iTunes Match. Once you turn on Match, you're limited to 10 devices total.

Is this what you want to do...same iCloud account, but different iTunes/App store accounts on each device? If so, you can do that also.