O365 Connector: can we sync Users and use Exchange Online (no local exchange)

currently we have a local exchange and a WIndows PDC. This system is syncing our users to Azure AD.
In the near future we want to switch to a ucs based AD Domain and want to use Exchange Online.

So i was thinking i can just sync our users to azure and use the mail-feature there. However Microsoft is telling me that i need a local exchange to manage specific AD Attributes and to do some administation on Exchange Online

It would be interesting to know how other customers are using a setup with a local UCS AD, Azure Sync (o365 connector) and Exchange Online. So if you have some experience i would be happy if you can share them with me

Here is what microsoft says:

Why you may not want to decommission Exchange servers from on-premises

Customers with a hybrid configuration often find after a period of time that all of their mailboxes have been moved to Exchange Online. At this point, they may decide to remove the Exchange servers from on-premises. However, they discover that they can no longer manage their cloud mailboxes.

When directory synchronization is enabled for a tenant and a user is synchronized from on-premises, most of the attributes cannot be managed from Exchange Online and must be managed from on-premises. This is not due to the hybrid configuration, but it occurs because of directory synchronization. In addition, even if you have directory synchronization in place without running the Hybrid Configuration Wizard, you still cannot manage most of the recipient tasks from the cloud. For more information, see this blog article.

Can third-party management tools be used?

The question of whether a third-party management tool or ADSIEDIT can be used is often asked. The answer is you can use them, but they are not supported. The Exchange Management Console, the Exchange admin center (EAC), and the Exchange Management Shell are the only supported tools that are available to manage Exchange recipients and objects. If you decide to use third-party management tools, it would be at your own risk. Third-party management tools often work fine, but Microsoft does not validate these tools.