"I'm not asking if the colors will retain their original sheen, side the satin will obviously govern. Just wondering if there will be a difference in final appearance at all between the two. Trying to maintain a very subtle two-tone looking finish."
Theoretically once the clear-coat is applied the sheen will be consistent. In practice this is sometimes true and sometimes not, at least within the scope of my typical overcoat number - 2, 3 or 4. Past that I can't say. There can be subtle physical and even chemical interplay between two different original finishes and the clear overspray, it seems. Do it with patience and moderate coats; just don't be surprised if some sheen differences are persistent. It's usually slight, if apparent at all.
(As W.C. Fields used to say: "if it first you don't succeed, try, try again. After that, give up - no use being a d**n fool about it".)