You can use it as a mouse controller but it only really works well for games you boot through big picture. The trackball games in the Atari Collection on Steam are terrible. The controls are all screwed up, even with a mouse or actual trackball, so it’s not going to help you there.
Honestly, I found it awful to use and shelved it after a few weeks. It requires a LOT of tweaking to make it work comfortably. There are layouts and setting profiles posted by community but I never found those totally comfortable either. My hands kept moving off the edges of the analog pads and my characters would suddenly stop moving.
It’s okay for l games with a “point and click” interface but that’s about it. Your better off with an actual trackball.