How to tell if a CD is Encoded?

All SACDs are DSD

some CDs are based off analog tapes that have been remastered in DSD

some DSD recordings can be purchased as CDs

we seem to be confusing the recording and mastering (which is interesting) with the final media (which is the relevant point of your question)

as far as commercial silver discs go its red book pcm or 128 DSD that's it! Standards are standards

@geoffkait - even the vinyl LP versions of those Stones records are pretty well regarded. DSD vinyl. Dude.
@folkfreak - as an afterthought, this goes to your point about the mastering v the final medium.

To which I’d add that you can also change how you listen to the final medium.  For example I listen to my red book upsampled to dual DSD, sounds better that way to me in my system

so to the OPs follow on question about ladder vs delta dig DACs, it depends 🤪

If a disc says "Remastered in DSD", doesn't that mean the contents of the disc are encoded in DSD?  If not, we really need to establish a lexicon.

@folkfreak -- you said you "listen to my red book upsampled to dual DSD" -- I don't understand.  If a disc is encoded as Redbook (16/44.1), that means a 16 bit sample of the analog waveform was taken 44,100 times a second.  How can you get better sound out of that track by upsampling -- aren't you limited to the resolution of what's on the disc?

Not at all @cheeg. Consider an analog pressing of an LP that says "remastered on a vintage Neve console from the original master tapes" that doesn't mean you're getting a tape, it just describes the techniques the mastering engineer used to create the final mix.

It's exactly the same in digital. When SACD first came out and DSD A/D became available it was a selling point to say "mastered in DSD" (such as the Rolling Stones issues that were mentioned) and many CDs and LPs were sold on this basis.

As to the value in upsampling -- agreed you cannot create information that doesn't exist but there is much logic to a higher sample rate in terms of the avoidance of the need for certain deleterious filters, and not least a better fit with your D/A. In a full DCS stack, as I have, you can try any combination of input and output rates you like and select what sounds best to you.