It depends if the router has any ability to limit users at all. Belkin does not generally have the most advanced software.
In any case you can not limit based on how the user connects. You would have to limit by mac address. Most pc nics use the same mac when they connect to 2.4g and 5g.
It would require a fairly advanced configuration to even partially do what you want. You would have to assign the 2 radios to different vlans and subnets and then you could limit by ip address range. You would either need a commerical device or load something like dd-wrt on the router. Belkin tends to not allow third party firmware so you may have to purchase a different router.
If it has the feature it is generally called QoS. Problem is most routers you can only limit the upload speed. The download speed is controlled by the ISP you can not undelete packets the ISP discarded no matter how smart the router is. To a point some routers can limit user traffic download but it only works with some application. It is highly unlikely the belkin has the ability to hard limit a users download speed to a certain value. Pretty much I have only seen it on asus and tplink factory firmware. Belikin may have added it but they tend the have much fewer feature than other routers.