Bloatware is a problem on Android, and it's not just a Samsung thing. Removing apps that have the Uninstall or Disable button grayed out in Settings has always involved sending ADB commands to your phone from a computer, which itself was always such a pain to set up. Thankfully, that has finally changed.
Codecs are like ZIP archives for media files. Rather than storing an entire analog sound file, the digital version is compressed to save space. The algorithm used to reduce file size is called a codec, as it encodes to digitize and decodes when it's time to play the file back. So as you can imagine, a better codec can lead to drastically improved sound quality.
On a PC, you can play sound from multiple apps at once. It's great, but it can also be confusing — there's a volume slider in each app, then the system-wide one, and probably another knob on your speakers. To avoid this dysfunction, Android only has one sound stream for media. But that has its own problems.