I think I got you confused lol. When you are watching a stream (for example if you’re watching Ninja play on his stream) you are downloading data, that would be the same as watching a movie on Netflix or watching a video on YouTube. If you are actually doing a stream, meaning you are putting your video to Twitch so other people can watch you then you are uploading data. Both uploading and downloading data counts towards a person’s data usage. Now which cap your internet company would count those 2 different things as, you would have to ask your internet company. My mobile internet cap count both as the same thing, they don’t have a separate one for Netflix or YouTube, everything counts towards my total, so your best option is to contact your internet provider and see what they say, every company is different.