Hi Adam, unlike the source backup job, it is recommended to leave inline deduplication enabled and set compression to Auto in the backup copy job. Veeam B&R inline dedupe requires the entire chain to be opened. In case of regular backup jobs, where only required objects are opened, disabling our dedupe gives certain performance gain. In case of the backup copy, where the entire chain is always opened, disabling dedupe doesn't play any role in terms of performance, while could allow for a bit better space savings.
Btw, here's the updated Veeam B&R/StoreOnce Best Practices guide
, which mentions those recommendations.