pfSense

Here is how to reproduce an issue where speed is reduced between internal networks where it should only be affecting WAN traffic.
You will need the following:
A switch capable of VLANs
A pfsense machine with 2 NIC ports where LAN is configured as a trunk between pfsense and the switch. The WAN port doesn't really matter for this test. You could connect it to anything... just so the link shows in UP state and ensure it cannot reach any LAN networks at layer 2.
pfSense CE 2.8 or pfSense Plus 25.07.1
Start with a factory default config, then add the following
1 WAN interface assigned to the first NIC port
Assign WAN IP or leave DHCP
Assign LAN IP and optional enable DHCP
Create 2 VLANs for internal LAN networks. I used VLAN 5 and 6 and assign them to the correct parent physical port.
Configure 2 access ports on the switch for VLAN 5 and 6 respectively.
Configure a trunk port on the switch for uplink to pfSense LAN port.
Re-assign the LAN to the second NIC port via VLAN 5
Create a new interface for LAN2 and assign to second NIC via VLAN 6.
Assign an IP to LAN2 and optional enable DHCP
Connect 2 hosts which have iperf installed; one on VLAN 5 and another on VLAN 6 via the switch access ports as configured earlier.
For simple testing, create an any/any rule so VLAN 5 can reach VLAN 6.
Start iperf in server mode on the host in VLAN 6
Perform an iperf test from the host in VLAN 5
Observe the test will complete at full speed of whatever your network links are between hosts.
Configure a traffic shaper using the multi lan/wan wizard and specify the following
1 WAN, 2 LAN type interfaces
LAN1 PRIQ
LAN2 PRIQ
WAN PRIQ, download 300 Mbit/s, upload 300 Mbit/s
VOIP leave default / blank
Penalty Box default / blank
Peer-to-Peer blank
Network games blank
Raise or lower other: Enable checkbox
Set a few things to higher and lower priorities just to get some rules and queues created and so the shaper will have something to do
Filter reload
Perform an iperf test again from the host in VLAN 5
Observe the test will complete at 300 Mbit/s