Really you should search the threads there is a wealth of information here.
Face painting makeup is for the most part quite opaque. How much you use depends on how you apply it. The better you get at application the less you use, and how much can vary by brand. And of course by the size of the container, some brands come in varied sizes from 15 grams to 70 grams of makeup. Any top brand cake activated makeup will work for cosplay.
As for powders they too can work but have less staying power. One god brand is Mehron's Starblend which was made for use as a water activated cake makeup but face painters have made using the cake dry very popular. Once the cake is wetted is is not usable dry, So you choose one usage.
Water activated cake makeup for face and body painting is not set or sealed with translucent setting powder. Only cream makeup is set with powder. Body paint cake makeup is set or sealer with spray fixer. Powder is not sprayed. There is no sealing powders. Although you can use fixers under the powder.
Makeup wears off in first in the places you expect. If the skin bend or wrinkles if it sweats or gets moist the makeup comes off there first - elbows, knees, underarms, under breasts, the neck.... Since you live in a humid climate testing is a good idea. Many face painters like the powders in humid areas. Honestly I not opt for this juts based on the difficulty of keeping it intact on large areas. If your moist if can be hard to apply initially.
Top brands for body paint, powders and fixers include Wolfe FX, Mehron (Paradise), Kryolan, Graftobian, just to name a few. Shop a local costume shop or order online.