I hope you can help me, I need to do a research project about this model of hyperbolic geometry. Honestly, I've never studied the subject, and I'm not sure that subjects should give more importance. Although I considered two issues:
1) Möbius transformations. 2) Distance and lengths.
Another issue to consider?
Thank you :)
Talking about a model, rather than the thing that its modeling, is a very narrow subject. The specific length formula, the way that angles are calculated within a model and the set of automorphisms for a particular model are pretty much the only particulars that one can turn one's attention to.
Regarding hyperbolic geometry itself, not specific models of it, the nature of hyperbolic triangles is probably the most interesting and easily accessible area of study, in particular the relationship between their areas and their angle sum.