Administration Exchange local admins

Depends on what exactly you want. Technically speaking, creating new mailboxes in O365 is done by assigning a license, which is an Azure AD operation. Thus you need the corresponding Azure AD/Office 365 admin role, and those are challenging to scope down to a subset of users. Best you can do in this regard is use Administrative units: https://docs.microsoft.com/en-us/azure/active-directory/users-groups-roles/directory-administrative-units

AUs are quite limited though, so don't expect wonders. Now, it you only want to delegate Exchange-related tasks (sans provisioning user mailboxes), you can do just fine as Exchange Online's RBAC model is very robust and you can create custom management scopes limited to a particular country or department. Pretty much the same procedures as with on-premises server apply.