Sorry for replying to something older in this thread (I'm still making my way through everything), but as someone who didn't get into SW until high school (right before the special editions came out), I didn't know that the actor who played Tarkin had passed. Watching the film, I couldn't tell that he was CGI, but there was an "offness" to him, not in the uncanny valley side, but that he felt like he wasn't "there" in the scenes, that he had been added in later.
So, I went in not knowing that the character would be in the film, not knowing the actor was dead, or anything. And while I didn't peg it as CGI, I did peg something as off. In 2D.
Leia, on the other hand, I couldn't tell anything with, and was disappointed that the credits didn't list her at all, I didn't know if it was heavy makeup on a look-alike or what.