I have emperor Tetras (palmeri). Can't say much. They don't seem aggressive. They pair up, which isn't common among the other Tetras I have. I have never kept pearl gouramis.
One thing I notice is that they tend to stay in the top half of the tank. It could be because there are many schools of smaller Tetras in the community, and so they have more elbow room there. They like the floating plants which also the dwarf gouramis I had liked. All my dwarf gouramis have disappeared or died. So the emperors have them to themselves now.