I used to have both enlargers and now have only the Zone VI Type II.
Type II negative carriers have dimensions 15 3/4" x 8 1/4". Type I were indeed smaller. The original Zone VI enlarger was designed as an oversized 4x5. So, the negative carriers for that enlarger were smaller, as one might expect.
As to the Type I being designated as a "5x7", somewhere along the line, things got carried away. It could never really enlarge 5x7. When Calumet purchased Zone VI, they developed the Type II to correct that discrepancy, enlarged the head, negative carriers, chassis, etc. They also built heads of the same Type II design that would fit the Type I enlarger. So, there are some Type I enlargers that can enlarge 5x7, but not using the original head.