Uaru and discus are very similar to each other in personality and parental care. Angels are laterally compressed like discus, but IMO the similarities don't extend to their behaviors or parenting. Having kept/bred discus and angels for a long time, I feel that angels are much more like Mesonauta. I started keeping angels when I was a kid and discus seemed like a natural progression at the time. Then I got my first discus and realized I was dealing with a whole new ball game.
I would love to read more about the evolution of South American cichlids but I don't have much to contribute. It is sad that we don't focus on those aspects of the hobby, but a thread about culling fish or who has the best festae ends up being 40 pages long. Maybe if we asked how many believed in evolution here we'd get a better response.