An enlarged atrium may be the cause of your
atrial fibrillation, but LAE may also develop or be worsened by
atrial fibrillation, so the cause-and-effect isn't always clear. PACs may also increase due to atrial enlargement.
The hypokinesis has probably nothing to do with your PACs. Different parts of the heart. Your overall EF is good though, so it seems like your pumping function is maintained.