I did UWSA 2 after NBME 6 but before the rest. I dont think it matters. I believe you should do the nbmes in ascending numerical order, and after that, sprinkle in the UWSAs however you want. I personally, however, would do the UWSA at least two weeks out. You need time to review those question and, more importantly, UWSA questions are trickier and may not represent the ideal line of reasoning necessary for the real test (you dont want to get yourself in the habit of overthinking so close to the test)