Hi
Can i have two clusters in the same datacenter, one cluster with two hosts using vDS and a single host using a standard switch?
Yes, you can have multiple clusters in same data center with different vSwitch configuration.
But I would suggest to have same/consistent configuration across hosts in 1 cluster.
The default Port Binding type is Static Binding which means you can connect a virtual machine to a static-binding port group onlythrough vCenter Server.
If you do not have port group with Ephemeral binding, you cannot connect a new VM to VDS if your vCenter is down/powered off.
For the vCenter port group, you can consider creating or editing the PortGroup that is used by vCenter from static port binding to Ephemeral port binding.
With Ephemeral port binding, you can assign a virtual machine (the vCenter) to a distributed port group on ESX/ESXi and vCenter, giving you the flexibility to manage virtual machine connections through the host when vCenter is down.
More about ephemeral port binding:
http://www.ecloudsol.com/blog/distributed-switch-port-binding-in-vmware-vsphere-5-0/
Lost vcenter with ESXi host and cannot power on with vDS | Virtual Me
If you need to edit VM settings on VM hardware version 10 but vCenter is down, you can also use PowerCLI
You can keep the vCenter in VM hardware version 9 if you don't need any new features in version 10 + prefer the VM to be editable via vSphere Client.
VMware KB: Downgrading the virtual machine hardware version in ESX/ESXi
Are you running vCenter Server from Essentials Kit license?
If not, you can also have 1 vCenter Server managing those two TestEnvironment.
No need to have 2 vCenter if you prefer to manage all the clusters from 1 vCenter - especially when the clusters are in 1 site/location