The iPhone's Settings app is usually the place to go when you need to make changes to how your phone behaves. Or maybe you need to access your iCloud settings, or tweak the Camera app, or the way the ...
You can delete apps on your Apple TV if you aren't using them, and then redownload those apps for free later.
Any recent Apple TV will have Netflix, as it's available on every Apple TV model except for the 1st Generation.