What is the speed you are paying for (upload and download)?
If you want a method that does not need any additional software, you can try the following. (works well if the client you want to throttle can only use a single band).
It is rare to find a router with no web UI at all, they will at least have some stripped down settings, especially for basic things like changing WiFi passwords and possibly doing some compatibility related tasks.
If wireless one option is to see if you can restrict the band being used by the device to an older standard.
Depending on the implementation, restricting the client to 802.11g speeds, will mean about 22Mbps if right next to the router, and around 10Mbps if in another room (in some cases,even if separated by just one wall).
If you have a low upload speed, and need to take extra steps to limit uploads, you can use the QOS controls built into windows.
In the group policy editor, go to Configuration\Policies\Windows Settings
you can then right click on the QOS option and create a new rule, and then just set a max speed for all applications. for both TCP and UDP.
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Another option is to cripple the WiFi performance on the client side through the advanced wifi adapter settings.
Simply pick a mode and disable VHT.
802.11b will pretty much limit the user to at best 5-6Mbps.