Wales are on the same points as Scotland and Croatia (17) and one more than Greece (16).
Points against 6th placed teams don't count so you're on 11 points with Scotland and Croatia. Greece are on 13 points and because their last match is Gilbraltar, they'll remain on 13 points.
A draw would take you to 12 points. Therefore behind Greece.
If Scotland win then they'll have 14 points. Anything less than a win and they'll be overtaken by Slovakia (providing they beat Malta) in the group who'll have 12 points and a better goal difference than Wales in the play off table.
The only way a draw is good enough for Wales is if Ukraine v Croatia also ends in a draw and it's not a higher scoring draw than the Wales match.
Apparently if Wales drew 0-0 with Ireland and Ukraine drew 1-1 with Croatia (or 1-1 and 2-2, 2-2 and 3-3 etc) then it would come down to fair play points, whatever the fuck they are.