Backup performance for single stream is roughly 30% faster when you keep source side dedupe disabled (i.e. "High Bandwidth" on the Catalyst Store GUI). Despite this, I keep suggesting using source side dedupe (i.e. Low-bandwidth mode) in production environments.
Working in source side dedupe, when your backup job contains about 10 VMs and you process them concurrently, you can easily see the throughput rising higher than 1500MB/s even across a single 10GbE link. When you add more jobs and proxy/gateway servers in the game, you can rise the throughput even further without being limited by the network connectivity.
It is important you make sure the entire data path is design for your expected throughput, not just the last link to StoreOnce. At these speeds, the primary storage could easily became a bottleneck as well.
An important suggestion is to pay attention that your Veeam Proxy, which is selected by the Backup-Job, runs on the same server (physical or VM) as your Veeam Gateway, which is selected by the Backup Repository. If the two services run on different servers, then your backup data does not go straight to StoreOnce via Catalyst, but there is an extra hop in LAN and that connection is not deduped.
In the past, I thought Catalyst could make high bandwidth reduction only for Full Backups, and my lab tests seemed to validate that behavior. Then I sow production environments achieving bandwidth reduction in the range of 10:1 to 30:1 even for CBT incremental backups. That surprised me, so I went back to my lab to check what was wrong... and the wrong part was my workload generator based on many 50MB files. Indeed, most production workloads are based on many small write operation and few large ones. When I changed my workload generator to produce many small and few large files, I sow a rising dedupe effect also for Incremental backups. Tests with just 1% of new data distributed over a lot of very small files were able to generate .vib as big as 15% of the full. This happens because even a few KBs file forces the CBT engine to mark as changed an entire 1MB wide segment in its VMDK. StoreOnce dedupe works at a much granular level and it identifies the real changed data inside the larger segment, and so it avoids sending the unchanged parts.
This long discussion to say that Source Side Dedupe helps also for Incremental backup and not only for the Full ones.