Using Lightroom CC with a NAS and no cloud

No, that is not right. When you create collections of images in Lightroom Classic and choose to share those collections, they are shared with Lightroom for the cloud and therefore are available on all other mobile devices. They are shared as Smart previews, not full-sized images. But they are large enough to be edited, and the adjustments made on those mobile devices, tablets, other computers will affect the  images in Lightroom Classic on the main computer where the master images are stored. The Smart previews do not impact your allotted cloud storage, so you have unlimited storage for these collections in Lightroom for the cloud.

Unfortunately it isn't possible Oliver.

The Cloid Based Lightroom does have the option to store originals externally, but this is a mirror of what is in the cloud and it's main purpose is for faster access to each photo (cuts downloading time if cycling through quickly) or for offline use.

The photos always reside in the Cloud.

Lightroom Classic would be the best option 

To put it plain and simple, it doesn't work that way. That's all there is to it.

I believe what he was suggesting is that if you want to use Lightroom with no cloud access then Lightroom Classic is what you must choose. Images are stored locally rather than in the cloud, and you don't have access to those images on other devices. But it does reduce the amount of cloud storage that you need.

Lightroom Classic uses local storage but to use it your LR Classic program has to have access to that local storage so there's no way to access those photos elsewhere on other devices.