Prefacing this with: "I don't know much about computational requirements or Unity backend crunching/churning."
However, NGUI has this wicked feature for Atlas-ing your textures into a nice big 'ol texture. A large 1920x1080 texture for just your static GUIs will be redundant with NGUI. Instead, cut them up and use the Atlas maker to make a nice 'only as big as it needs to be' image. Then, add these Sprite using your widget tool to your UI. Since they all come from the same atlas, the performance will not see a significant hit by putting in your static sprites.
You can create empty GameObject 'roots' that you can parent all your health bar related stuff too (sprites, labels, buttons, and all).