All images have to have the same size? No. The photo collection can have different sizes, but the application will set the render with the size of the first photo and cut every other photos to that size.
Do the photos have to be taken from the same position? No. But it helps. If you take photos by hand and shake a bt, when they blend, it will be blurred, so i might fight sync the photos to same position in another photo editing software. You may have photos from different positions on propose to make something you want. That is great and shows that you already have more art in your blood than any of us.
What is maximum number of photos in a collection? 16.777.216 photos in theory. In practise the limit is your computer memory. But keep in mind that TimeShot doesn't impose any limit (other than almost 17 milion).
Why do the canvas photos have such a bad resolution? Allowing such a big number of photos we had to trim down the fat so the application even moves. We defined a resolution to the canvas, but that can change in future: maybe depending on the number of photos on the collection or be configurable.