I had 3 DL TATL tickets in W fare this year. All segments were in W (AF operated TATL flight) or Y (DL/AS domestic and intraeuropean) classes.

On DL domestic I got immediate upgrades after V/X availability appeared.

On one ticket there were equipment changed on CDG-ATL route from AF to DL hardware and was downgraded from AF Premium Economy to DL Economy Comfort (Y class). Tried to upgrade with miles but was declined that fare was not YBM.