Yes, 190 pixels is 190 pixels, BUT when you deal with long strings of text, or even small strings of text when tabling, your monitor will wrap that text automatically when it gets to the end of a line (and a line's length depends on your resolution). Images, if not tabled properly, will also wrap under each other at lower resolutions. This wrapping effect is what will make a signature seem perfectly fine at one resolution, but not fine at a lower one.