Explanation
https://helpcenter.veeam.com/archive/backup/110/hyperv/guest_interaction_proxy.html According to the Veeam Software Help Center1, Veeam Backup & Replication deploys runtime components on a VM guest OS to perform file indexing. These components can be either non-persistent or persistent depending on whether you have enabled application-aware processing for the VM.
If you have enabled application-aware processing for the VM, Veeam Backup & Replication uses a persistent agent component that is installed on the VM guest OS during backup job session and remains on the VM after that. In this case, if the guest interaction proxy is offline, Veeam Backup & Replication will use another available guest interaction proxy or fail over to the backup server.
If you have not enabled application-aware processing for the VM, Veeam Backup & Replication uses a non-persistent runtime component that is deployed on the fly and removed after indexing is complete. In this case, if the guest interaction proxy is offline, Veeam Backup & Replication will use another available guest interaction proxy or fail over to the backup server.

You can use Veeam Backup & Replication and Veeam Agent for Microsoft Windows operating in the managed mode (within the Veeam Agent management scenario) to create backups from native storage snapshots.
Native storage snapshots allow the following:
Veeam Backup & Replication to use backup proxy servers to process storage systems.
Veeam Agent to use hardware Volume Shadow Copy Service (VSS) provider and capabilities of native snapshots that are created on production storage systems to create backups.up.
https://helpcenter.veeam.com/docs/backup/agents/storage_systems.html?ver=120

In a scenario where backups need to be sent from Site B to a repository at Site A and the direct backup cannot complete within the backup window due to connection limitations, a Backup Copy Job is the most suitable type of job. The Backup Copy Job can transfer data efficiently and with reduced impact on the production environment. The components involved would be:
6 (Repository at Site B): Where the initial backups are stored. 4 (WAN Accelerator at Site A): To optimize the data transfer over the WAN. 3 (WAN Accelerator at Site B): To prepare the backup data for transfer. 2 (Repository at Site A): The target repository for the backup copies. This configuration leverages the WAN Accelerators to reduce the amount of data that needs to travel over the WAN, thus allowing the backup copy job to complete within the available window.

Explanation
https://helpcenter.veeam.com/docs/backup/vsphere/vbr_config_migrate.html?ver=120#step5 The "Migrate" mode is designed specifically for scenarios where you need to move the Veeam Backup & Replication server and its configuration database to new servers or locations. It ensures a smooth transition without data loss or service interruption. This mode allows you to migrate the entire configuration seamlessly.

To protect a physical Windows server running Microsoft SQL 2020, the Veeam Agent should be used. Veeam Agent is designed to provide comprehensive backup and recovery for physical servers, including those running critical applications like Microsoft SQL Server.