It all really depends on your client and your exact project. But in the past, we have always had separate QA and UAT Environments. We the goal is to have one mirror projects but I have never actually seen that happen.
It is had to do user testing at times but usually this is done running the end application or use some type of simulated test files.
As far as BAM, I’ve not done too much with it so I’m not sure they best approach.
Hope this helps.