I've never been good at interpreting EVC tables, and now I'll need to know if there are some limitations to vMotion from/to Intel Xeon 6144 (Sky Lake) and 6244 (Cascade Lake) CPUs.
The vSphere release will be 6.7 latest update available or 7.0.
Thanks in advance
EVC support for Cascade Lake has been added in vSphere 7. You won't see the EVC level like that in vSphere 6.7 as the maximum supported one is Skylake.
However for vMotioning VMs between the two servers you will need to use EVC on Skylake Level so you can add your Cascade Lake supported servers and they will take the EVC level.
As @lalegre said it should be vSphere 7.0 (watch out for VMware HCL and be careful with that)
EVC should be in skylake in the cluster.
If you have an "older" cluster with another version, let's say Haswell, it should be lowered to haswell in both clusters in order to support cross cluster vmotion (if you don't use it, don't enable it)
Hope that works.