Need help modeling for articulation and low poly

Hello again Y’all. I’m trying to make a character mesh that can be used for complex limb articulation, but especially for complex facial animations. Also I want to have the body morph from female to male, and from skinny to fat using shape keys. My mesh so far:

In the first picture you can see I’ve made two different head meshes. The one to the right seems like it’d be better for eyebrows moving up and down. What do you guys think?

I’m also having trouble with the hand. I want to bridge that gap but I haven’t found a good solution that doesn’t add problems with topology ( making weird bumps that don’t look like knuckles). I don’t want to add a lot more geometry to the hand, any thoughts?