There is no simple answer to this question, but I shall do my best.
Toei Animation originally animated the movies in a 4:3 aspect ratio (equivalent to the square-ish size of a typical old-style television set.) However, they intentionally animated the movies with the intention of being cropped, so as to fit onto Japanese theater screens. In other words, they were very careful in animating the movies, so that no details would be lost when cropping for a theatrical exhibition. All theatrically-release Dragon Ball/Z/GT movies were, indeed, cropped for their theatrical release, but animated from the beginning by Toei knowing they would be cropped.
It gets even more confusing with the American DVD releases. Early American Dragon Ball/Z/GT movie releases were in a 4:3 aspect ratio. Usually in America, this is the aspect ratio associated with cropping a theatrical movie to fit an old square-shape television set. In actually, the OPPOSITE is true.
This is Toei's original 4:3 animation, BEFORE it was cropped for Japanese theatrical exhibition. In other words, these versions actually had MORE picture than the Japanese official theatrical releases! However, as was previously stated, these movies were created with the intention of being cropped for widescreen exhibitions, so these movies actually had more picture on the screen than was ever meant to be seen.
The latest "double features" released in America of the Dragon Ball Z movies properly crop the movies back to their Japanese widescreen exhibition aspect ratio, and are enhanced for viewing on widescreen televisions. At long last, American audiences have the "properly cropped" versions that only Japan has had for years.
However, one of the double features was of the Trunks/Bardock specials. These originally aired on TELEVISION, in a 4:3 aspect ratio, and were intended to be seen as such. That said, this double feature HAS been cropped, and is no longer in its proper original aspect ratio intended for viewing.