I've been doing the 5/3/1 as described in 5/3/1 2nd edition. For assistance, I use the Triumvirate. I'm making excellent progress every month.
But every month I have the same question, and I re-read the relevant sections of the book and spend an hour or two looking through the forums for an answer; this month I thought I'd ask it in the forum.
Week 4 is the deload week, and the sets and reps are 40% x 5, 50% x 5, 60% x 5. But this feels silly since I just finished the warmup sets, which are 40% x 5, 50% x 5 and 60% x 3.
So, I end up doing different things every month. Tonight, I just did the work sets, then went to the assistance exercises.