Is this a correct principle for designing vSAN on HPE Synergy?
At least one SSD is required for caching in each VSAN.

A customer has a Microsoft Hyper-V virtualized environment. You are helping a customer replace some of the hosts with an HPE SimpliVity cluster.
Is this a correct guideline for adding and managing the new cluster?
Use the Deployment Manager with Microsoft System Center Virtual Machine Manager (SCVMM) to add nodes to SCVMM one at a time.

Is this a correct principle for designing vSAN on HPE Synergy?
Drives for storage pools should use RAID 6.

You are proposing HPE Synergy to support a VMware vSphere environment, in which clusters of ESXi hosts provide high availability for workloads such as a web farm, an inventory server, and a database.
Is this a recommended design principle for this use case?
Set the BIOS workload profile for compute modules that will be ESXi hosts to one of the virtualization profiles.

Is this a reason to implement VXLAN on an HPE FlexFabric or ArubaOS-CX switch?
to integrate with VMware NSX and provide wider support for tunneling between VMs and physical machines