You don't need two PC's to stream to be a successful streamer, but it does have 2 big advantages:
Dave 'Rojo' Jong is a professional Fortnite player for Lazarus. He can also be found streaming on Twitch.tv regularly.
For gaming, Rojo uses a Intel Core i7-5960X CPU with a NVIDIA GeForce Titan X Pascal GPU. He uses a ASUS X99-A motherboard. Rojo uses CORSAIR Vengeance LPX 32GB memory and a Samsung 860 Pro 2TB SSD for storage.