Do I need to angle/pitch pex tubing for draining in the winter?
yes you do.  even if you drain it, its going to get water lying in low spots.  that will rupture the line if it freezes.  just make sure you slope it 1" in 4 ft to where you are going to drain it.  that way it will have no water in it come freeze up.  you can just mount it with stood off pex clamps