anatomically correct AND emotionally correct
You've definitely hit on something with that. As i was drawing those two pages I realised once again that even in a photo, hands can look pretty awful and "unrealistic" for certain poses. So to some extent, manga/art is not drawing things correctly, but drawing things to look correct.
For me my worst hand poses are the OK gesture (or any thumb to finger pose) , and just an open palm pose. I just can't get them right for some reason haha
I always use photo references to draw from, but a lot are ones I have taken of myself. Partly thats because I don't have a decent mirror setup to get the angles that I want, and mostly you will be drawing hands from the opposite angle that you look at your own hands. I need to take more references with interacting with props.
I also use manga reference to see how other artists simplify the body and hands, but I try to not use it as reference too much since it is pretty low quality.