Bluestacks! If you know how to root it and make it solid, it's the best out there IMO. They just launched a beta version with Android 11 so that puts them in front of everyone. I have my own setup for an experiment and I've tested it all, literally, all of them: Nox, Memu, Android OS, you name it, all of them. So far, in terms of scalability (with resources costs) and flexibility, Bluestacks has the leading role. But, as I've said, I've chosen it for the main reason of scalability cause if you start putting Android OS one next to each other to run something, you will get lots of conflicts for example.