I very much dislike pistol grips. I don't blame them, but more of a personal preference.
Also, as a test, try having somebody wiggle/rotate the gun while you hold it with a pistol grip. Now rest thumb on top like a traditional rifle. Compare your results. I found it's much more secure holding it the traditional way.
That being said, when I shoot my rifle I grip very little. I apply pressure straight back with my finger tips on the vertical grip of the Whiskey 3, then try to pull trigger straight back. Something that I have to remain mindful of.
Everybody has something that works for them.... My method of shooting is definitely prone/table set-up. PRS positions/situations will be a steep learning curve for sure.