I thought some might be interested in the results I got from a little research at
Canada Post:
In Admail Picture Postage (not lettermail or publications mail) there are:
3 formats: horizontal, stamp-like and vertical
3 categories: regular, dimensioned, oversized
2 languages first: English, French
2 options: no return, return postage guaranteed
Here are the 12 English-first options: (There are another 12 French-first ones)

The no-returns are regular & dimensioned.
The RPG's are regular & oversized. (only difference is in the QR Code)
I was fooled for a while by all the different sizes (in my collection) until I saw that a company can vary the size of the indicia within the format:

The French-first indicia is like this:

A slightly different selection is available for Lettermail:

and for publications mail:
