I’ve bought two Denafrips DACs new (Venus 2 and Terminator plus) and they definitely settle in after some use, but certainly not a dramatic night and day. They have always sounded good out of the box.
I run mine on OS fast filter, very hard to tell a difference between fast and slow OS in my experience. NOS sounds more analog but loses detail and air. Lastly, I really like the AES output versus the others. Bass is more full, sounds more natural, and has just as much of everything else as USB.