pfSense

What I see on both 2.7 and 23.05.1 that applying an upload bandwidth limitation for Allowed IP Addresses has little effect but a download limit seems to work, though possibly irregularly. With an upload limit set but a download unset, the result was about a 10% speed reduction. With the download limit set and upload unset, I'd see iperf on the client receiving at just under the specified limit (150 Kib/s). Fast.com in Firefox would show well above this (tens of megabytes), but still limited and nowhere near the result if no limits were set at all (nearly 300 Mbps of my ISP plan). Setting both an up and down limit results in the same behavior as with just a download limit.

Setting the Per-user bandwidth restriction on the portal's Configuration tab, and limiting by MAC address both still work fine. Other than a portal zone name and turning off authentication (click-through was still necessary), the portal settings were left default and I set the bandwidth restriction to 150 Kib/s. Client was a Linux virtual machine behind a pfSense VM. Client was given a static IP address and set to use pfSense for a gateway and DNS.

Fast.com results were:
16 Mbps with limit 150 Kbit/s down, up unset
28 Mbps with 150 set for both both up and down
270 Mbps with 150 up, down unset