I think, and I admit that this is just speculation, that it's a mix of Spiner wearing an improved version of the Data makeup and some digital de-aging but not an entirely CGI character. Data's face in the new pictures looks rounder and softer, closer to how Spiner's looks now, with a much less prominent chin. So if any de-aging is applied, they seem to mostly be using it to smooth up Spiner's face and remove some of the lines, which the makeup also helps to do, but no, I don't think they're using any sort of prosthetics (except for the contact lenses) or lots of CGI (because why not make Data look closer to how he did 17 years ago or even before that?).
EDIT: For the sake of the original question, I (like the OP and most of the fandom) am assuming that Brent Spiner is playing Data here and that while this Data might use the body of B-4, his neural net/memories/etc are the same as the original's and as such I've elected to refer to the character as Data.