Yes, it's not so straightforward because as you say, some rows decrease across the row (rows 3 and 6) and some increase to bring you back to the starting number of sts (rows 4 and 7). The decreases for the neck are going to be on alternating 4th and 2nd rows, so sometimes they will be on knit rows. For the times that they aren't, it's easiest to skip one pattern repeat and just knit the sts, putting in the decrease along the left edge. I would put a movable marker on the needle at 17sts from the left edge (one edge st plus the 16sts you eventually want to decrease) and make sure that those 16sts decrease by one on the alternating 4th and 2nd rows.
So when the dec is on row 2 or 5, skip the first yo. If the dec is on row 4 or 7, skip the twisted knit st and just k1. If the dec is on rows 3 or 6, which are already decrease rows, I would move the decrease to the next row, either 4 or 7 and k1 instead of *k1, k1twisted*.
You may have to see how this looks in the pattern st as you go along.