I did tests on the MOX that show there is no performance degradation purely because of VLAN-traffic without NAT: MOX wired throughput issues
NAT-traffic automatically reduces this possible traffic because of involving the firewall.
The figures you share seem reasonable to me. A Turris Omnia for sure can reach full bidirectional gigabit NAT ethernet throughput (without traffic shaping, but I believe that’s nothing you after thinking as of now, right?).