That is helpful, ThanksFor me it has to do with appearance of the continuation of the lines of the pen body, nib and then the angle of the tip. Very subjective.
In your picture, FOR ME the bottom one doesn't stick out far enough and the second from the top is out a little too far. The other two are in the right ballpark.
A good reference to try. ThanksMe too. I kind of go by how they look - just a personal preference. I find that replacing rollerball refills with Pilot G2 Gel refills sometimes affects how far the refill extends too. - Dave