Well it's difficult to say with certainty from just a few pictures.
From the top three, I wonder if you are deliberately holding the hand straight. In a world without gravity, the ideal would be for the hand to be in line with arm, which is what it looks like to me. A lot of people, myself included however, will let the hand relax and fall to a slight bend. Nothing extreme. The fingers seem a bit splayed out compared to mine but that's probably just differences in our hands.
I can't really tell from the last shot because it doesn't show the upper arm, but I'm worried that you might be bending at your wrist. Viewed from above (players perspective), the arm and the hand should be mostly in a straight line, maybe a slight, very relaxed bend.
Comfort is important and within certain parameters, a good indicator that you're getting it right. You certainly don't want to do painful stuff. Do try to keep hand tension at a minimum. Another indicator is, how does it sound? If it's not sounding right, something's wrong. Out of all the potential positions and movements that the hand can assume, I think the ideal is to choose ones that get us the sound we want, when we want it, without discomfort, and with efficiency.
I think you made a good observation when you stated they all seem to have different forms. A lot of people get teachers who can obviously help, but I think in the long run we all make our own technique. If you're going it alone, in addition to what you're already doing, get a method book. It'll be more systematic and it'll teach you to read notation that the vast majority of CG repertoire is in. There are some available for download on this site, although you might have to meet some posting requirements.
Hopefully somebody with better credentials will chime in.
There's one in every crowd.