This is maybe a heads up for what I found.
My Xbox is used on a TV which only does 720p resolutions. When I tried streaming to windows 10 it looked a bit horrible. My display settings on the xbox were set to auto detect the TV connection. When I changed the settings on the Xbox manually to 1080 instead of auto detect it looked fine when streaming. Streaming seems to match the resolution of the TV its connected to when its set to auto detect rather than the possibly higher PC resolution its being streamed to.