Azure AD Connect Hybrid Join AD

@Edy Thanks for reaching out. I will answer your questions point per point.

I understand that once Hybrid Join AD is configured in AAD Connect, the selected(scoped) containers containing Computer accounts will be Synchronised to AAD and the Computers will automatically join AAD?

Yes, all the machines which are in scope will be joined to Azure AD as Hybrid Azure AD joined.

If servers are also in scoped in Synchronisation Service, will they be joined as well?

Yes, if they are in scope, they will be joined as well. Here is the official document abut mentioning the same : https://video2.skills-academy.com/en-us/azure/active-directory/devices/hybrid-azuread-join-plan#windows-current-devices

Also, this is how a server would look as well if its hybrid Azure AD joined : (I used a DC to do that but it is not recommended. This was my test lab)

If the Computer Accounts are not in scope in Synchronization Service, will they also attempt to join?

No, the computers which are not in scope will not be hybrid AAD joined.

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