I invented the idea of Wanda Prime as a joke weeks ago asserting that the power had nothing to do with Magneto - thus Magneto Prime was dead a while ago... demi just wouldn't believe me. He took my Wanda Prime and tried to face off against Phoenix. I thought I'd see where the thread led and I'd say it's safe to assume Wanda is right up there. I'd put her above Franklin Richards in sheer power, possibly Abstract level in terms of sheer power - considering to remake 616 reality to your desire is as if 616 Eternity - as the embodiment of the universe - was a dog and you said "I like cats better." so you turned it into a cat.
I just happened to notice the incongruity between the two assertions, which really still stands. From what you're saying now you are in fact still implying that the character Jean Grey with all her history etc is unnecessary to the Phoenix. In which case it's not so much the character Jean Grey = Phoenix as the Phoenix Force = Phoenix, and the character Jean Grey is still superfluous to it's existence, and it took her memories and likes to look like her.