Would it be easy to implement https://github.com/uWebSockets/uWebSockets with super powers to create a multiplayer game runnning on nodejs?

Actually will be easy since it depends on the server, so if you want to use uWebsockets on Socket.IO it should be configured (here someone talk about that) on the server, but the client will be the same no matter it uses ws or uws. That is if you use SocketIO, using other websocket client will require writting the apropiate plugin for that but still the uWebsocket decision will remain on the server.