@adamk11 How many and what type of NICs are you using? Are we to assume that pfsense LAN, and all VLAN's share the same physical port or do you have them separated?
If they are using the same physical port, I'm thinking traffic will go.
Generally speaking though, my experience from Proxmox using X520 NICs and VirtIO, I don't see any limitations in that regard. Running iperf between two FW's (over WAN interfaces) I get 8+ Gbps. I do have NIC's passed thru (IOMMU) to firewalls, but not to VM's.
Just now tested between two VM's in different VLAN's reaching 9.33GBit/s without any problems whatsoever, both VirtIO.