I know it says I can only field one copy of of each unique squadren card. Does this mean I can only field one xwing squadren in luke Skywalker squadren? Or more because all the xwing squadren have his art on reverse side.

You can only run one Luke Skywalker because the name has a dot in front of it - the pictures don't matter, only that dot.

Only 1 Luke

and only 1 squad will be Luke