Questions about ultra wide (21:9) monitors

Hello! Seriously thinking about buying a monitor, 21:9. But stop some differences, namely: 1. Many talk about divine the experience when watching movies, but they're all in 16:9 or something I don't understand? Found no movies in that aspect ratio. Even if you watch Blu-ray, there the same 1.77:1 is obtained, not 2.33:1.
2. As these monitors are combined with a blind people? My eyes are at a distance of 30-35 cm from 20'' monitor, as a result me a little that he would have to recede back to view all content.
3. The use of video and streaming services. Did I understand correctly that there are only two options: either crop the picture horizontally or sit with black stripes?
4. And, like, the last. That performance? it is obvious that the increase of pixels - increasing the load on the gpu, but how much will decrease performance.
PS happy to hear about the pitfalls of such relationships.