The most aggressive severums I own are the mouthbrooders, H. severus or H. sp. 'Atabapo'. My notatus are similar to greens and golds... you'll get aggression during spawning and they may occasionally get pushy about food, but mostly they are passive and ignore non-severum tankmates. The smaller you get them, the better chance you'll have of socializing them. I know some people buy young severums and raise them out with more aggressive SA and CA cichlids, and you end up with more aggressive adult severums. None of mine are like that, though.
You should be fine as long as there's no spawning. And even then, they'll most likely just chase your angels rather than murder them. I've had mine in with wild Peruvian angels, and I've also kept single females in my discus tank, and I've never had any immediate problems. My females in the discus tank were hogging food and I eventually had to remove them, but it wasn't actually an issue of aggression.
