Second, are you sure about this? My understanding is that if you use third-party tags such as analytics you need to get consent from users and not to use them if they don't consent.
One other thing that is not clear to me is if we need cookie prompts, and how can we implement cookie opt-ins/outs without being able to set cookies.
If you do linking of such stuff (like Google Analytics with DoubleClick) you need an opt-in. Only then the opt in cookie banner is really necessary.
Please excuse the late answer - was on holiday.