Searching advice - Slow restore speeds towards PVE?

[HenrikS.]

When restoring to PVE, we see slow transfer speeds, approx 500Mbps.
There are no obvious reasons for it, dual 25GbE links, no other running jobs, system capable of delivering 10+Gbps to VMware and PVE hosts have no load and NVMe disks.
Looking at metrics, I see that 1x CPU core on the Veeam AiO Windows 2022 is maxing out while running restore and no other jobs.

So, question: is the function of restoring to Proxmox VE single-threaded? Are there other obvious tweaks to implement?
Also, is it possible to change MTU for the Proxmox VE workers, as we see 6x performance increase due to interrupts handling in firewalls that lie inbetween by switching from 1500 to 9000