What's the difference between Python built by MSC and Python built by GCC?

I'm a Windows user. I used to install the official CPython from python.org. But recently I tried the mingw-w64-x86_64-python offered by MSYS2.

The two interpreters show different banners at launch:

• python.org: Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:37:02) [MSC v.1924 64 bit (AMD64)] on win32
• MSYS2: Python 3.8.3 (default, Jun 17 2020, 06:11:06) [GCC 10.1.0 64 bit (AMD64)] on win32

This tells that they are built by different compilers.

My Questions

1. What's the main differences between the two implementation from a user's point of view, especially those relating to package installation?
2. With the GCC version, I can install packages using either pacman or pip (I used pacman to install pip since pip was not included by default), which one should I use for package installation? In fact, pip failed when I tried to install packages like numpy, pandas and jupyter, pacman could install them but I don't know if there are any compatibility issues.