Posted on 07 August 23 at 15:53, Edited on 07 August 23 at 15:54 by bblcreator8790
I'm not 100% sure on this, but I would think that you will still get the achievements from the stack. For single player, you could wipe your save on the X/S version before transferring your last-gen save just to be safe, but I'm guessing that wouldn't even be necessary.
For multiplayer it would probably allow you to download your Xbox One character in addition to whatever one you already have on the X/S version, though I believe you can only have two characters max so you may have to overwrite one if you already have two on the Series X/S.
FYI you could also stack the Japanese Xbox One version if you want while it's on Game Pass; most of the MP is pretty quick after doing it in the regular version; both Xbox One versions share multiplayer progress but requires you to redo some stuff, but it's not too time consuming. Though you would have to do single player again.