About fact it could be on board. Yes, it could be there. It is really a kind of basic questions but they are also rarely found or google. First of all as a recommendation for every one for any topic: "Google it first. Search on forum. Ask if still didn't get an answer"
Usually always sprite sheets consist of frames with the same size. So the size of frame should be enough to contain any of frames
If you work with a frame size 32x32 and your character in general occupies 26~28 pixels so you can not to crop it and it doesn't matter how it aligned +/- pixel to right of left.... What is really important that every frame must be aligned to other frames of all the animations