AFAIK, you need to use seperate drives and install the OSes in such a way that each drive has its own EFI partition. (Installing with the other drive disconnected is the easy way.) Then only use your UEFI boot selection menu to choose which drive to boot from.

https://github.com/Bladez1992/LTSConvert

It is highly unlikely you will be able to hear a difference.

https://trac.ffmpeg.org/wiki/Encode/MP3

If you have golden ears or are just that worried, why not use a lossless codec like flac?

The company that made my TV is engaged in copyright infringement, you say? Transmitting copyrighted images over the Internet for profit?

Huh.