Minecraft.
There used to be a rudimentary port of it to barely run on old raspberry pi’s. Modern Raspberry Pi’s are good enough time run the actual game (albeit barely). It’s also frequently hacked with, cloned, and demaked, and is the most popular game on the planet.
Why use mouse when type very fast?
Vim actually has pretty good mouse support too if you turn it on!
The multiple power supplies are for redundancy. It will work with one plugged in but you are “supposed” to plug in both.
It’s fundamentally not that different from a consumer desktop. Plug in a monitor and a keyboard and a USB with your preferred flavor of headless Linux installer on it. Configure ssh as the first thing you do because you won’t want to plug the monitor and keyboard into it every time you need to tweak something.
You can probably find VGA to HDMI adapters if you can’t find a monitor with VGA support.
Dishonored is a lot like Deus Ex but fantasy themed. 10USD right now (20USD for the bundle with the DLC but the DLC isn’t really necessary).