This is a complex question and and can't really be answered by a "Yes, that's correct" or a "No, do it this way instead" response. The "right way" to design the hierarchy structure is dependent on a lot of business decisions and needs that aren't shared in the post (and likely shouldn't be publicly). There's a few things I can recommend, though:
- First, read about what a management group is. It'll help you group subscriptions logically in ways that you can apply Azure Policy definitions, tags, and do cost management in ways that make sense to your business through inheritance and rollup.
- Then, check out the Cloud Adoption Framework and specifically this page: Management group and subscription organization. This will help you identity and ask the right questions to land on the right design with both management groups and subscriptions. To take this a step further, use the Microsoft Assessments tool to analyze where you are today on this journey.
- Lastly, check out Azure Resource Graph to help you quickly inventory your resources across all of the management groups and subscriptions within your tenant.
/David