Hi @ferdis ,
If you are referring to vCLS (vSphere Cluster Services) VMs introduced in 7.0 U1, they will work with 6.7 hosts. If you have 6.5 hosts ensure that the hardware version for these VMs are kept at version 11.
Hope that helps
I have information that even its possible and supported to run vCenter 7 U1 DRS Enabled Cluster (using vCLS vSphere Cluster Services) with ESXi 6.7 its not recommended. Anyone could elaborate on this and explain reasons?
There is a note here about 6.5 ESXi hosts --> vSphere Cluster Services (vCLS) in vSphere 7.0 Update 1
If you go by that, 6.7 hosts should also be supported for this feature