On the Managed Instance, all databases within the instance are located on the same SQL Server instance under the hood are just like on an on-premises SQL Server instance. This guarantees that all instance-scoped functionality will work the same way, such as global temp tables, cross-database queries, SQL Agent, etc. This database placement is kept through automatic failovers, and all server level objects, such as logins or SQL Agent logins, are properly replicated.
The new Azure Database Migration Service (ADMS) is a fully managed Azure Service that enables seamless migrations of SQL Server instances from on-premises to Azure Database Platforms with only a few minutes of downtime.