1. Aren't USB sticks used on TV sets to stream live (playback recorded content on USB sticks), if no transcoding is needed?
2. While we are on the subject, is it true that UPnP cannot do live streaming, i.e., can only stream recorded (library) content?
And for live IPTV streaming you would need a UPnP alternative like IPTV for Sony PlayStation 3 - xupnpd ?
3. So...how do you download Youtube type content from LE/Kodi into your USB stick?
A live stream and a playback from USB stick are two different types of transmission. Content providers want to give the same user experience, but technically it's different.
UPnP AV can do live streaming.
I have never recorded YouTube content, no idea.