Install size depends on the features you pick when you install. Web / service / library development is small, desktop / mobile / C++ gets bigger as the toolchains + sdks + emulators are big. If your VS install is 30 GB and that's a problem, run the installer, click modify, and uncheck stuff you're not using. A lot of devs check off everything "just in case" but since you can add other features when you need them, it's better to start with what you know you'll use.