I have an MR600 to provide internet in my house in France as the landline connection is very poor. With an external aerial this is giving me download speeds of 60Mbs+ which is great. However French data packages have monthly limits and even with the biggest package I can buy (250Gb per month) we are eating through the data very quickly. The problem is that most streaming services seem to automatically dowload HD if there is enough bandwidth. This consumes something like 4Gb an hour which is why we are using so much data. Given that all the screens are small we don't need the high resolution and SD is fine. I can see that I can control the bandwidth of individual devices by using the QoS but we have lots of people coming and going with their own devices so I can't keep adding them. 

Can I set a global QoS for all devices and limit individuals to say 3Mbs? That way the streaming services will default to a medium resolution which should ony use 1Gb an hour.

I can see that there is a global bandwidth control on some tp-link routers that will manage a range of IPs but I can't ee the same funtion on the MR600