I’m confused about this, are you going to put the flame angel in the DT or the sump with the PT?
I’ve had a few flames in the past and they were not crazy aggressive with the other fish but they did pick at things. One ate a clam and I don’t remember exactly what else they ate but they were a pain in Arizona to catch and that’s what I remember about them most. I can’t see the future and I’m not familiar with your family of fishes so I can’t say how they will react to a flame addition.
Best wishes. If there is living room in your current tank it may slide in almost unnoticed but since the purple was evicted I would bet that the flame will end up in the sump, tattered and worn out from the fight in the DT. Hope I’m wrong.