pads and discs. they are already vented, no reason not to get grooved too. brembo max are my preferred, they do make them in the right size and bolt pattern but I'm not sure they are listed for the micra. I like pagid fastroad pads but they are insanely expensive these days. Rears, a good service is all they need and adjusting correctly, they aren't the prime stopping factor on the car but a good service will ensure that you aren't wasting effort pushing fluid to poorly set up drums that could be doing other work in the system. after that it's replace hoses (don't rush out and spend a fortune on braided, unless you plan to keep the car for 10+ years they wont feel any different to new rubber for that time). you'll be bleeding the system at this point, which will make the most difference of all, 5 year old brake fluid is garbage and one of the biggest reasons for spongy and poor brakes, it's also insanely easy to replace.
the brakes on there are more than good enough for the weight of the car if serviced correctly.