Yes I could be wrong but I thought that one or more movies were re-rendered for fullscreen with characters repositioned accordingly to suit the framing, not just the camera reframed in general. If it’s true then I’m sure it varies by shot with the minimum amount of work possible. Feel free to post any caps.
Edit. Also in this vein, were any releases actually done from film prints or were they all done from master digital files to NTSC? If they can put it on film they can put it on video, I don’t see why they’d use the in-between.
Okay, the only one officially confirmed by Pixar themselves where they reposition objects or characters to fit the screen was for the 4:3 versions is for Bugs Life (optional on the 2003 2-Disc DVD). On Disc 2 for the 2003 DVD, they made a bonus feature about it and compared it next to the Theatrical widescreen version. The only other movie where I’ve noticed repositioning is for Cars but only for like the opening like for the front graphic effects like when they’re showing clips of the characters alongside the race and that news scene where McQueen is missing. Otherwise, I haven’t seen any repositioning for any of the other Pixar movies.
Also, to answer your other question, all of these 4x3 releases on DVD are from the digital files, not film reels. If we were talking in general though, the only one that wasn’t from the digital files was Toy Story for the original 1996 VHS release, instead based off a film element for it’s source.