Xbox Music Pass on Windows 8

Hey Guys,

I think about getting the Xbox Music pass but have a question and hope one of you has an answer.

I am curious about the "offline" feature you get with the paid pass.

But how does the app actually store the tracks so you can listen them offline?
Are they downloaded as mp3 files or something like that on your pc?

Wouldn't it be cheaper if you get the music pass and download whole music albums instead of buying single tracks?

I am no nativ speaker but I hope you know what I mean :D