Jordan 1 G is the same width as regular Jordan 1, but the sole is slightly longer. Jordan 1s are going to be more wide foot friendly than Air Max 1s... and most Air Maxes in general. So in your case with narrow feet, you should size down. However, if your toes are touching the tip with 11, then go with 11.5.
Jordan 1s while it may not be the best leather, it's still leather. Over time with use, the leather fibers do loosen, but this can take a long time... depending on how much you wear them. If the width is snug, consider half size up if your feet tend to swell by the end of the round. You could wear them casually the break them in more. As long as you're not the type that drags their feet, the treads will be fine.