No right answer, no wrong answer.
Depends on the pistol, caliber, load, distance, casual or match shooting, and the individual definition.
As Bullseye is my choice of shooting disciplines, I'll address your question from the one handed shooters perspective.
First, my definition of the grip. The semi auto should be pinched between the center section of your second and third fingers and the section of the palm between the base of the thumb and the life line in the palm. Think of your hand as a vice and you are pinching the front and back of the pistol with your "vice". Your finger tips should not curl around to press against the side.
The little finger should not grip the stock. It is very hard to establish consistent tension with all 3 fingers and the little finger is WAY down at the bottom of the lever (if you think of the grip as a lever) where it induces the most effect with the smallest amount of variation.
1911-45ACP. Grip until your sights start to tremble then slack off when the sights stop trembling. Having an inconsistent grip makes shooting a pistol virtually impossible. I have found the hard grip is easier for a new shooter to use consistently. After, you have a few thousand rounds down the bore you will settle on YOUR best grip, not necessarily MY best grip. I have shot with Master and High Master shooters that grip the gun so gently I swear it would torque right out of their hand, but it works for them. I no longer grip the 45 really tight.
22 semi auto. Duplicate the 45 at first, however the learning curve is faster on the 22 due to the recoil factor. When I shoot Free Pistol or International my grip is very light and almost gentle. But those disciplines are all slow fire, and loaded a single shot at a time. The pistols also have very light crisp triggers. When I shoot timed or rapid fire the grip is harder.
For "TARGET" revolvers, the grip should be gentle. EX: 32,38,41,44,45 target loads around 600-750 fps. This of course should not be done with heavy hunting or silhouette loads, those must be gripped tight in order to not have to remove your front sight from being embedded in your forehead.
If you have any 'good' Bullseye shooters in your locale, search them out and ask questions. NOT DURING A MATCH or during a string of fire. Like any shooting discipline I have ever tried, they are extremely helpful and share a wealth of information to get a new shooter shooting well much faster than trying to learn it all yourself. Don't try to reinvent the wheel.
FWIW