Personally, I do not think that copying other Youtube channel ideas is the best option out there. Some creative guy, who knows who was it now. Invented the "Let's play" series and it got famous. Everyone saw how famous it is and rushed back, copying it. Why would you try to be a copy? Personally, I try my best to be as original as possible. I might do some known series here and there, but still. I, at least, do not follow the same structure as other people. If people who are subbed to Leafy see your video. Why would they watch you over Leafy when he is the original guy who knows exactly how to do this properly because it is his idea in the end.