most the people who watch these streams are probably 8-13years old the same as all the "famous" youtubers you see there fans and it's all kids mostly.
most be fairly embarrassing as an adult being mobbed by kids
Again, depends upon the streamer, Cohhcarnage is a very famous streamer, so much so that he has a cameo in Cyberpunk 2077, but very few of his fans are kids at all but thats down to the way he presents and the content he provides (which has a far far greater appeal to adults than kids in its style and content). So it really does depend upon the streamer themselves, the likes of Dr Disrespect and Asmongold may well have a largely young fanbase but the likes of Cohhcarnage, Quill88 and itsmeJP have far older fanbases. Just as in many forms of entertainment , there is a wide range of entertainers from the fart gag Ade Edmondson/Rik Mayall types to the more cerebral Stewart Lee types. Streaming isnt really much different in that regard.