In what format, and over what kind of ethernet? You can stream video uncompressed (or something lightweight and lossless like hufffyuv) but at that point the bandwidth requirement becomes significant, both on the network connection between the two PCs (hope that's separate from your stream upload) and within the bus on the gaming PC, and encode/decode is always going to add latency (obviously less of a concern for a non-twitch game). It's definitely doable, but connecting the video out to a capture card (duplicated to a screen where you're playing) is generally going to be the better option, that way you're using all the hardware the way it's designed for and everything is normal as far as the gaming PC is concerned.