You don't need two PC's to stream to be a successful streamer, but it does have 2 big advantages:
Kevin 'Noizeeh' Jaskiewicz is a professional Fortnite player. He is currently the team captain of Method’s Fortnite roster.
For gaming, Noizeeh uses a Intel Core i9-9900K CPU with a NVIDIA GeForce RTX 2080 Ti FE GPU. He uses a ASUS ROG Strix Z370-E Gaming motherboard. Noizeeh uses G.SKILL Trident Z RGB Series 32GB memory.