Hi,
1) The Vcore required is CPU dependent.
2) The set Vcore and actual Vcore will be different according to LLC.
3) Some CPUs benefit from de-lidding/re-lidding, and using better thermal paste. Usually, you can get an extra 100-150MHz overclocking headroom from the CPU, due to lower temps.
4) To answer your question, yes, on the Apex my CPU will do 5GHz with less than 1.40V, quite easily.
-Raja