Quest198z Regarding control over networking components (VNETs etc) located in application landing zone subscriptions ... if you require any further restrictions on top of what is recommended in the ALZ design, you can use a combination of AZURE Policies and RBAC.
The platform landing zone is documented in detail on MS LEARN: What is an Azure landing zone? - Cloud Adoption Framework | Microsoft Learn. There is no such thing as a connectivity landing zone though. I believe you are referring to the connectivity subscription? This is one of the subscriptions, part of the platform landing zone, that hosts all platform networking components. For the sake of completeness: there can be multiple connectivity subscriptions in a landing zone. This is documented on MS LEARN as well.