Not all turtles need UVB. However, those that don't do need supplemental D3 in their diets to help them process calcium and other vitamins and minerals. Will you be providing light, heat, a basking area, any structure in the tank? Muds and musks don't all bask, but there are individuals of every mud, musk, and snapper species that bask voraciously. If you're going to deal with pig-nosed turtles, you need to invest in a good heater. Even turtles that can brumate need to have the right temperatures to do so successfully. If it gets cold, but not cold enough, they can get sick and die without ever actually going into brumation. I would recommend just getting a heater no matter what you go with, but then again you probably don't want to have a huge power bill.