I'm pretty sure your team can find a particular style that suits for both of them, the game is easy on the first stages but then enemies start comming from everyplace and it turns a pandemonium LOL. I hope you find a way to reorder the UI accordly to screen size.
I don't use Unity, but i think there should be a way to implement something like relative coordinates calculating screen size and tile the UI anchoring the elements relative to those calculations. These calculations are not so hard to set i hope you find a way to do this. Also i think you can set a small letter related to it's actions in the UI, i.e. setting 1 for the first skill and so on.
Good luck!