Hello Julian,
The part of Windows that I work in is responsible for quality updates. Unfortunately, that means I'm not an expert on feature updates (new builds). I know the feature update team has done work in windows 1709 and 1803 to shrink the size of feature updates using the same express technology we use in quality updates. If you haven't already seen it already, this looks like a pretty good resource for different deployment techniques for feature updates
https://docs.microsoft.com/en-us/windows/deployment/
Sorry I can't be more helpful on feature update questions. If you have a service contract your account manager should also be able to help you work through a detailed plan that is specific to your environment and challenges on getting devices upgraded.
Mike