How the DR & synchronization works b/w the Datacenters when Datacenter 2 is not identical or similar as DC1 in terms of available nodes and partition data? Or is it mandate that both DCs have to be identical and similar in terms of hardware, nodes…, etc.?
The capacity and worker node topology has to be maintained on both sides, i.e. you could have 10 worker and 2 standby nodes on the primary side and only 10 worker nodes on the DR side. But reducing the number of worker nodes on the DR side is not supported today.
How to size the Bandwidth between the Data Centers using Synch and Asynch modes?
This highly depends on your RPO requirements: the longer an outage and data loss you can accept, the lower the bandwidth might be. A higher bandwidth certainly reduces the RPO in an asynch scenario.