Creating an UV map for my dragon model


I’ve been working on a project for learning purposes and the project itself contains a dragon - my latest goal is to add my dragon model to UE4 and try to learn more about state machines and if I’m competent enough, perhaps try to create some simple game on my own. As you can see I’ve got very ambigous plans… :wink:

However, right now I’m trying to create some nice UV maps for my creature so I could easily texture it and this is also the place I need your suggestions/tips/help (what could I do differently if I should).

I’ve separated my model into three parts - headbones, the body and the wings. I also have eyelids, eyeballs and pupils as separate objects, which I haven’ t unwrapped yet. I’m clueless how I should create my UV maps - should I add all parts of my model to one UV map or not?
The second question is - how large should my UV maps be?
I’ve purchased Substance Designer and Substance Painter software to texture my model if it’s neccessary to know.

Apparently I can’t add pictures of my wings UV maps because of the pictures amount limitation. I’ll add picture of my overall model instead then.