I doubt twitch shooters would be playable. I've used steam's in home streaming, and platformers that require precise jumping accuracy are basically unplayable because even a fraction of a second hiccup in latency can get you killed. Even simple platformers like Crash Bandicoot can get frustratingly difficult to play over a stream. If the service gets popular enough, we might see developers making changes to help out players using Stadia, the same way that they add auto-aim for most console shooters, but disable it in the PC version.