I have a RBTA with clowns and anything else I wanted: Tang, Coral Beauty, Leopard Wrass for fish and all kinds of soft, LPS, and lower light SPS like Seriatapora and Montipora.
My anemone did move when I originally placed it and did sting things along the way. But everything it stung recovered and once it found it's happy place it has not moved again and has been in the same place for 4 years.
Now brown star polyps are actually encroaching on the anemone's territory and causing it to retreat. I wish it would sting the BSP more than it does.
I think the biggest problem with anemones is that most people ,when they're counting how many fish they have in their bioload, forget that those anemones poop and blow their reproductive stuff into the water and dirty things up worse than some fish. You need a large enough tank or a commitment to keeping it really clean to keep them happy.
Once your tank is stabilized and they've found a good spot, they usually don't move. But if you change currents, lights, or you have big swings in your water quality they have more tendency to roam.