Yeah, the background removal for both the C992/x and the Stargazer, even, are both kinda sub-par. I don't think software-based solutions will ever be as good as hardware ones. That pretty much goes for anything, though. That said, hardware will ALWAYS do what software can do, better. At least when it comes to this field.
A physical green screen will always be better than any software-based solution, is basically what it boils down to. But if you plan on using a software solution, unfortunately, after using both the C992 and the Stargazer now, it's still looking like the Logitech seems to do a better job.