Of course, you can use them in each period of the war. The uniform wore by those figures was kept till 1945. Moreover, even the M1934 uniform was delivered to troops till 1945.
So use them without any hesitation. I have also these sets and I intend to use them in a Normandy dio. Just remove the stips form the arms of the figures that are in Set1 if you use them in another period than 1943.
I noticed that most of figures form set 2 are slighty smaller than those from set 1. They are not at 1/76, but there is a small difference, mostly seen at head and weapons. But it doesn't matter they can be used on the same dio.