We have plan to configure two clusters.
One cluster will be current cluster with vSphere 6.5.
We will upgrade the current vCenter from 6.5 to 7.0.
The R 730 server from old cluster will remove from current cluster.
Upcoming R 750 new server and R 730 server will be in new cluster.
There will be two clusters, old (vSphere 6.5) and new (vSphere 7.0).
My questions are.
If I understand your question correctly, you currently have a 6.5 cluster, where you want to take out a couple of Dell R730 servers and add them to a new cluster. In this new cluster, you would then add in new Dell R750 servers afterward?
You would have 1 vCenter 7 instance to manage both clusters and the old cluster would stay on 6.5.
This is perfectly possible, you need to make sure to enable EVC on the new cluster or you will not be able to add in the R750 servers and move your VMs. Set EVC to the highest supported level of the R730 servers, this will depend on the CPU you have in there.
One final note, vSphere 6.5 is no longer supported and you should consider moving away from it entirely