Registry: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\Setup

The value of CachePath specifies where package manifests and, optionally, payloads are stored.

The default is %ProgramData%\Microsoft\VisualStudio\Packages

SharedInstallationPath specifies the directory where some packages across versions are stored.

The default location is %ProgramFiles(x86)%\Microsoft Visual Studio\Shared

https://devblogs.microsoft.com/setup/moving-or-disabling-the-package-cache-for-visual-studio-2017/