Hi SyenceLabb,
As far as literature goes, you can find a lot of the official documents at StorageHub.vmware.com Here is some info about DD/C Storage and Availability Technical Documents
The Dedupe ratio/efficiency will depend on many variables, such as number of VMs, amount of unique data, number and size of disk groups, etc. Although DD/C is enabled at the cluster level, it dedupes and compresses at the Disk Group level during the destage process. If 4K blocks cannot be deduped/compress to smaller chunks (<=2K blocks), then we don't waste resources trying to dedupe/compress for a tiny gain in space.
Now, the temporary overhead you are seeing is the space "reserved" while objects are being moved. See KB for more info VMware Knowledge Base
Hope this helps