I have small interference in chan 100 here.
WIFI is doing 1.75 Gbits/sec 
2401.9 Mbit/s, 160 MHz, HE-MCS 11, HE-NSS 2
2401.9 Mbit/s, 160 MHz, HE-MCS 11, HE-NSS 2
AX210 laptop: iperf3 -c -t 30 -P 2
AX3600: iperf3 -s
Test#1: wlan1 gro ON + Packet steering ON
(no IRQ optimizations, NAT SW offload ON but not relevant in this test)
Server result:
[ ID] Interval Transfer Bitrate
[ 5] 0.00-30.01 sec 3.10 GBytes 887 Mbits/sec receiver
[ 8] 0.00-30.01 sec 3.00 GBytes 860 Mbits/sec receiver
[SUM] 0.00-30.01 sec 6.10 GBytes 1.75 Gbits/sec receiver
Test#2: wlan1 gro ON + Packet steering OFF (+reboot)
[ ID] Interval Transfer Bitrate
[ 5] 0.00-30.01 sec 3.00 GBytes 859 Mbits/sec receiver
[ 8] 0.00-30.01 sec 3.06 GBytes 875 Mbits/sec receiver
[SUM] 0.00-30.01 sec 6.06 GBytes 1.73 Gbits/sec receiver
Test#3: wlan1 gro OFF + Packet steering OFF
root@X2:/# ethtool -k wlan1 | grep generic-receive-offload
generic-receive-offload: on
root@X2:/# ethtool -K wlan1 gro off
root@X2:/# ethtool -k wlan1 | grep generic-receive-offload
generic-receive-offload: off
@robimarko here we can see the diff it makes with GRO ON or OFF:
So this diff will be more visible in cpu limited 2.5 or 10Gbit like you said.
(...and I'm only using WLAN in this test)
[ ID] Interval Transfer Bitrate
[ 5] 0.00-30.03 sec 1.93 GBytes 553 Mbits/sec receiver
[ 8] 0.00-30.03 sec 1.75 GBytes 500 Mbits/sec receiver
[SUM] 0.00-30.03 sec 3.68 GBytes 1.05 Gbits/sec receiver
Test #4 - Not related to the previous tests:
A --bidir test, to show that WIFI isn't FULL-DUPLEX and to point out what @joba-1 was saying.
(Same conditions as test#1 that gave 1.75Gbit in one direction only)
AX210 laptop: iperf3 -c -t 30 --bidir
AX3600: iperf3 -s
Server side results:
[ ID][Role] Interval Transfer Bitrate Retr
[ 5][RX-S] 0.00-30.01 sec 2.83 GBytes 811 Mbits/sec receiver
[ 8][TX-S] 0.00-30.01 sec 2.90 GBytes 830 Mbits/sec 0 sender
