I ran an Alien on the second floor of my house with a NG Powerline in my audio room for about 6 years. Two weeks ago I added a second Alien (as a mesh) in the audio room (needed more ports) and removed everything else.
The up/down speeds increased and I have way fewer dropouts. There was no change in sound quality, just better performance. Not sure how Eero compares to Amplifi Alien products but changing to mesh was a positive for me.