To change the resolution of the stream you’re watching press the “Auto” button on the stream overlay.
You can then change playback to the resolution you want to watch the stream in. All available quality options for that stream will be available as options.
Autoplay makes it so that as you scroll through streams in the watch feed they will start playing to give you like a sneak peek into the stream without entering the channel. Autoplay is enabled by default, but are able to toggle this off in the settings screen that appears as a gear on your profile picture.
When you go into settings just toggle off “Enable Autoplay” and it turn the feature off.