I've only had Maxis so can't say for the other various sub species but I can definitely agree on the individual personality part.
Nerd was shy, timid, and kept away if he didn't know you. He was my best friend and I was his world. He liked my sister and they had certain things that were only for them but once I got home it was hang out with dad and get scritches and treats as requested. When he left me I got Lurch, a very mad at the world and scared used parrot. He would just suddenly bite without warning and was aggressive but after slowly working with him over 5 years he got closer and closer till I begrudgingly earned his trust and he chose me. He was still a grumpy boy so I avoided him when he was in a mood or learned to be fast. He was finally happy with his lot in life. He escaped in early 2016 and I was given Dobby when Momazon could no longer keep him because she had followed what I went through with Lurch and thought I'd be a good dad for him. He's the most socialized, outgoing, mischievous boy I've ever known. He loves everyone he meets and will always step up when asked. So they all have the usual similarities but each one was their own unique soul.
Nerd spoke wild Pionus and I spoke it back. He had a wild jungle flock call that could wake the dead BUUWEEEEEP!
Lurch could talk, sometimes very clearly, most times like a drunken pirate. He had phrases he already knew and weird foreign sounding words and he was picking up new ones from us.
Dobby loves to say DOBBEE, I'M DOBBY, HI, DOBBY GOOD BOY, etc, usually in my voice however his favorite thing is whistling and noises.
Talking has never been a requirement but it's cool if they choose to seeing how they aren't known for it.
They make very loyal life long friends once they choose you.