What is the difference between the two versions?
32A and 32u4 are all commonly used MCUs on keyboard PCBs.
The 32A version PCB can be easily re-programmed with a software called bootmapper client. bootmapper client has a GUI and is straightforward to use. It can run on Windows OS and OS X.
The 32u4 version PCB can be re-programmed with QMK/TMK. QMK/TMK is an open-sourced code framework written in C/C++. It's more powerful but has a steeper learning curve than bootmapper client. You will have to install a lot of dependency packages on your computer, compile the source codes, and flash the hex file to get the firmware updated. It can be compiled on most Linux distributions, Windows, and OS X.
The 32A version can also be programmed with QMK in theory. I won't bother to port the code tho.
The 32A version we provide in this GB comes with USB mini female connector. The 32u4 version comes with USB Type C female connector. The Type C connector is a little better than mini on the design perspective in my opinion, not that good you need to throw away a fancy Yarbo cable to get this version tho.
TL; DR: You are a newbie, you are lazy, choose 32A version. You write codes, you are cool, choose 32u4 version.