If you are the kind of person who streams Netflix in ultra HD all the time then you will only be able to use one device at a time since it takes 25 Mbps to run Netflix on that quality. Individuals or small families are good sizes for 25 Mbps, you can still stream at lower qualities, surf the web and check emails all at the same time. A larger family would have a hard time trying to stick to a 25 Mbps download speed if multiple kids were wanting to stream. The size of the screen does not matter for how much data it uses. It depends on the service you are using, and because each service is different in the amount of data it uses it is good to know how much it is for each service. For example, Netflix’s highest quality is ultra HD at 25 Mbps while Amazons highest quality is at 15 Mbps. You would be able to stream more on Amazon compared to Netflix if you paid attention to how much data they used. You could use a couple of devices at most if you had 25 Mbps, if you go over the download speed limit though your devices will start to slow down so watch out for that.