And how does ESXi 7.0 install relate to pfSense ?
You ought to do a better 1'st post.

Btw: 7.0 removed the linux subsystem , rendering ALL realtek-drivers useless.

/Bingo

@maverickws

have you checked iperf3 speeds between pfsense and xcp-ng itself?
Mine is bad. Additionally from pfsense to xcp-ng it has many retries during transfer

@wyattwic Yes, qemu is not kvm, however it tends to do all the dirty work, like bios emulation etc and then sends the code to kvm for execution, if there is such option, or emulates it.
It would be interesting to see performance differences between hardware virtualisation and emulation on such a heavy ι/ο related system such as pfsense.

Problem solved. You need to set "Westmere" or "kvm64" CPU type instead of host passthrough in libvirt/virsh/kvm/qemu configuration file "virsh edit $vmname"

<cpu mode='custom' match='exact' check='none'>
<model fallback='allow'>Westmere</model>
<topology sockets='1' cores='6' threads='2'/>
</cpu>