All three films are open-matte, only the effects shots were letterboxed. The FX were shot in VistaVision, at a wider AR - some of the live plates for FX shots were also shot Vista to reduce grain buildup on composite. So for example, if you look at a print of BTTF II, the full frame will go from open-matte to letterbox every time the same actor appears in a shot twice.

The DVD framing issues were utterly baffling; wouldn't locking the transfer at frame center to match up with the letterboxed FX shots have provided the correct framing? Was there wiggle room in the FX hard-matte shots? Are they not actually centered on the frame on the film sources they used? Still a mystery 13 years later...

And is the "DCP" version truly the raw 2002 transfer? Did the original DVD also have the digital cleanup gaffe that turned Marty's skateboard wheels from yellow to pink?