Yes you will need alignment. ANY TIME YOU REPLACE/OR TAKE OUT ANY SUSPENSION PART(EXPECT SHOCKS) or Steering parts like Tie rods or the rack;.
i agree. having done alignments for years, i can say that there's up to 0.7* of camber adjustment in many strut assemblies. do the mounts first then do alignment.I would get the strut mounts done now and then get the alignment. As long as you are planning on getting the alignment done, do all the suspension work first.