There are only 31 picks in the 1st because the Patriots lost their pick.
I can also guarantee you that more than 3 CB's and 5 DE's go in the 1st.
Ramsey/Hargreaves are obviously locks, Alexander is probably a lock as well and then you have guys like Apple and Jackson who teams will certainly fall in love with due to their size/speed. Then at DE you have Bosa, Buckner, Spence and Lawson who are all 1st round locks, on top of Dodd, Bullard and Ogbah who are likely to go in that 1st/early 2nd range as well.
To me, it's much more likely that a guy like Apple or Dodd goes in the 1st than a guy like Austin Johnson or Kenny Clark.