In its update FAQ, Instagram explains that now videos will be preloaded for autoplay, something loathed by some users--especially if that autoplay will include ads that use their 3G and 4G bandwidth. Instagram even acknowledges that while preloading makes videos start more quickly, it also uses more data.
So the part about data usage controls means that you can get auto preloading to stop at least some of the time by choosing to have videos preload only when you're connected to Wi-Fi, thus sparing your data plan.
In addition, Instagram just posted a guide on how to refine the presence of audio in those videos. The Mute setting on iOS or the Sound setting on Android will let you control what you hear.
Oh, and the latest update also lets Android users straighten their still images in the app, a feature already present in the iOS version. Instructions are conveniently located in the same FAQ.