V-Ray 3.3 significantly changed the way that the sampling algorithm works. If you were familiar with older version of V-Ray, you remember the amount of tweaking and adjustments were commonplace. This is no longer the case.
It has changed so much that initial Sampling lesson of Grant Warwick’s Mastering V-Ray course, is no longer relevant. You can throw it out completely. Instead, Grant Warwick replaces the old, with this new tutorial. It shows how to work with the new Sampling settings in V-Ray 3.3.
This is a great watch, as it shows how V-Ray operating sampled in the past, compared to how it is handled in the latest version. By the way, Grant is using 3ds Max as a host, but V-Ray is pretty much the same, no matter what host you are in.
If you are not familiar with the Mastering CGI series, it is the arguably the definitive V-Ray rendering training available.