I'm only just getting started with it! But yeah you need nether quartz for observers, which can look at blocks and do something if they change appearance. Sculk sensors on the other hand listen to blocks and do stuff if they make noise. I'm just trying to do a really basic bamboo farm that harvests the bamboo whenever I need fuel for my furnace but I need some way to tell when the furnace needs more fuel.

(I'm going to end up developing a whole new redstone theory at this point between being in Peaceful and putting off going to the nether. But it's neat to have to solve the puzzles in a different way that everybody else does.)