One of the stupid charts just like this had my pistol shooting fucked up for the longest time. I finally discovered that it made no sense to manipulate your grip and wrist angles to accomplish the very arbitrary goal of having the forearm and bore in alignment.
It's nonsense. Ignore it.
The way to establish a proper grip is to address the strong hand first. Get as high on the gun as possible. If you have a beavertail, the web of your hand should be forcefully squashed into it. Figure out where you want your trigger finger to fall upon the trigger and rotate your hand around the circumference of the gun as necessary to make your trigger finger be in the right position to manipulate the trigger. Verify you can access and manipulate all the controls from that position, i.e. slide release, mag release. Let me reiterate, it doesn't matter what the angle between forearm and bore is.
Now flag your strong thumb up. See all that empty space on the side of the frame and grip? You want to fill that area with your weak hand. Experiment, almost like your hand is a puzzle piece and you're looking for the best position in which to fit it. The general rule of thumb (pun) is that you want to be as high as possible again with weak hand and you don't want to interfere with the controls. I find that I get best results by slightly canting my wrist and putting the meaty part of the thumb (drumstick) up against my strong hand. You want your hands to mate together strongly at the rear of the grip without fighting each other for position. Now wrap your weak fingers around the fingers on the frontstrap. You apply force, or pressure against the frame and grip in 360 degrees. Note that I was specific with that language. I do not want to "squeeze" the grip, I want to apply "pressure" and cause friction between the grip and my hands that cause my grip to not shift under recoil. You will likewise want to experiment with grip pressure but the rule of thumb is that the weak hand applies more force than the strong hand, because the strong hand also has the job of pressing the trigger, which requires dexterity.
If you notice, the common theme in all this is to EXPERIMENT. No one's hands are shaped exactly alike of have the same grip strength or body geometry. You will have to make your own grip that works for you. But the fundamental principles apply- grip high, grip hard, grip in a way that causes you to be able to access controls and not cause malfunctions.
The elbow thing is really a comfort thing for me. I like a slight bend.
Good luck, and be free from the tyranny of the charts.