How to determine which release of a CD to purchase

[No Regrets]

Hello,

I've been dedicated to vinyl over the last 50 years. The sound quality of vinyl records is highly dependent upon the pressing quality and the mastering and of course the which run it is.

I am now in the process of upgrading the digital side of my audio system. I am wondering how to determine which cd releases are best to pursue.

I have just purchased a Jay's Audio CD transport and a Mojo Mystique X 24 AM NOS Ladder type dac. These will not play SACD layers but should be able to play the Redbook layer of a SACD disc.

I understand that most people would agree that the SACD layer should sound better than the Redbook layer of the SACD disc.
What I am asking is this... would the Redbook layer of a SACD disc sound better than just a Redbook Only cd disc of the same performance.

Or maybe another way to look at it.... is the mastering done differently and/or better on the Redbook layer of a SACD disc than that of a Redbook Only cd disc of the same recording?

Are there other parameters to look at when purchasing a CD. What should I be looking for when I go onto discogs searching for music?

I appreciate everyone's patience with me as I am trying to learn and understand the digital side of music.

Best wishes,
Don