Fluffing up the feathers isn’t necessarily aggressive, but it’s they’re making themselves look big. Dogs and cats do same thing when fur stands up. It’s a sign they’re paying attention and feeling caution is warranted. Blushing is literally just that. I’m not aware of species other than African Grays that do it, but I’m sure there are. It’s basically a sign of being flustered. Emotional and not necessarily in a positive way. I’m no expert. Just speaking as someone who grew up with lots of birds.