@MiroKostovBG
PAL and NTSC have different resolutions.
Perhaps when you are running PAL games, the screen output is resized to fit the extra vertical lines (576) onto the screen and that 'squishes' in the sides a bit. NTSC only has 480 lines.
You can probably eliminate the top/bottom black bars with overscan settings, but it seems like the left/right bars will likely always be there when playing a PAL game.