Greetings from Viovio. Most of our templates are fixed sizes by the template designers. This means that you can adjust the crop within them, but cannot adjust the template drop-zone itself.
We do offer an auto-fit template in each of the ratio's that will allow you to drop 1 or more images in and the template and it will automatically fit the images without trimming. You can easily recognize the autofit template because it has an icon of a magic wand on it with sparkles, and it's over what looks kind of like grey cinderblocks.
If you have any further questions please let us know and we'll do our best to help!