As for performance, Yarn is about 3-5x faster installing all of the dependencies and devDependencies of react-native. The benchmarks are here: https://yarnpkg.com/en/compare. It's much faster in most scenarios, especially the ones that used to take minutes.
The benchmarks test both the hot cache and cold cache scenarios for npm and Yarn. Except in the scenario when node_modules is already populated and there is no yarn.lock file, which is uncommon if you're using Yarn, Yarn is faster than npm in all of the benchmarked scenarios where there is a cold cache.
