You don't need two PC's to stream to be a successful streamer, but it does have 2 big advantages:
OhMyPulse is a full-time Youtuber and Twitch.tv streamer. He is currently focusing on Fortnite.
OhMyPulse uses the SteelSeries Apex Pro TKL gaming keyboard.
For gaming, OhMyPulse uses a Intel Core i9-9900K CPU with a ASUS ROG Strix GeForce RTX 2080 Ti GPU. He uses a ASUS ROG Strix Z390-E motherboard. OhMyPulse uses G.SKILL Trident Z RGB Series 32GB memory.