Packages are by developer: lexx83 (Alexpux), mingwandroid, niXman. MSYS2-shell uses "pacman" for downloading packages from repo, and these are GPG signed & verified. MSYS2 is a successor of MSYS and MinGW-builds.
It supports & can work with both 32bit & 64bit multiple toolchains & targets, (for 64bit a 64bit operating system is needed). It includes: MSYS2-shell and MinGW-w64 Win32 shell & MinGW-w64 Win64 shell. MSYS2 and MSYS2 (Minimal SYStem 2) is an independent rewrite of MSYS, a (command-line) shell for development usage, and based on modern Cygwin (POSIX compatibility layer) and MinGW-w64 (from "MinGW-builds"), with the aim of better interoperability with native Windows software.