I just bought an Oxygen 25 (3rd Gen) at the thrift store. Is there anything I need to download over at the M-audio site n install on my Mac? Or is it just plug n play? I'll be using it with Pro Tools 12.4 if it matters.
As you could find out yourself by doing a simple check on M-Audio's homepage: "Oxygen 25 is class compliant and does not require an additional driver for the selected operating system."
The only thing you'd need to download is the DirectLink mappings if you use Logic Pro X (or GarageBand) as a DAW, and want to auto-map the knobs and buttons.
Most other DAW's have DirectLink built-in with recent versions. Check this page for details: