>>3228298There is no correct answer to this. You have to take it on a photo by photo basis, and decide if it looks ok cropped to a square, if it's ok to crop a tiny bit off the ends for a landscape/portrait shot. If the answer is no then you go with white borders. You don't need to make the borders big enough to fit on the square, just make the border the aspect ration instagram likes and then stick your photo on top.
A standard photo will fit in with just a small white area above and below.
So tl;dr look at your photo and decide what works best for it
