Your plan looks ok to me, here are some things to consider:
* If possible, I would aim to have another physical host, that can be used as restore target if the primary fails.
This host doesn't need to be as powerful as the production host, but needs enough storage and RAM to allow restoring and launching at least the most important VMs to it, in case you need to restore in a timely manner and not only to backup.
This host can optionally be used as replica target in addition to regular backup jobs to qnap.
single cpu with 4 cores.
16gb ram (or more if possible)
single or several SATA disks.
OS = same as production.
* Regarding networking, I suggest the following:
Veeam management (sql and GUI) can be either on VM or the host, or if you have another physical server then on it.
However the backup process itself should better be executed by the source host (on-host mode), for best performance in your case.
You can use the management NIC on the host for that purpose.
On the QNAP side you won't get special benefit from teaming both NICs, so you can provide different IP address to each NIC and then target specific NIC on QNAP from the source host. The other NIC will be idle from Veeam point of view, but available for other tasks.
For example, you can dedicate NIC1 on QNAP for management and CIFS traffic, while the other NIC2 dedicated for ISCSI.
Above is not a bottom line solution - just an optional config to consider with both PROs and CONs vs your plan.