Gaming on the PC is more complicated and offers more options than on a console. Every game is different in how it uses game controllers, mice, and keyboards.
Every game store, like Steam, Epic, Battle.net, XBox, etc (there are more than twenty), do it differently, and do it differently in different games.
There is no single answer for how to use the Quadstick and/or other controllers with all of them.
On a console, nearly every game will play the same way using the same controller. That is just not the case with PC gaming.
The closest to a "standard" is most games, not all, that accept a controller will work with the XBox 360 controller emulation on the Quadstick. Most, not all, will also work with QMP 4+ emulating an XBox One controller, but that is more complicated to install and set up.
That is all just the connection between the quadstick and the PC.
You can plug
many different devices into the back of the Quadstick. Using a
Brook Wingman XE plugged into the USB-A socket allows over 125 different controllers, including the XAC, to bring their inputs into the Quadstick to be used in the configuration, as if they were a Playstation DS4 controller.
Example test configuration.