320kbit/s Opus. It's pretty okay, but there's some compression (in the audio sense) going on, so that some songs sound very noticeably worse. Tool for example lost all its, well, toolness.
I think you do need an account (which could be trials) because you have to use an ARL or your credentials to login to Deemix with.
I personally pay for a Deezer family plan and just use offline play mainly for my car.
From what I remember MP3DownloadNet uses the Deezer API to download MP3s and FLAC. I used to collect music with this site before it all the ads but it seems like it's still working.