Not surer that Onomah is overrated. He's probably rated about right for what he's shown against people in the same age group. He's dominated youth football.I genuinely always thought Edwards had the air of a massive douche about him, right back from when Sherwood first named checked him all those years ago. He comes across as someone who was hugely gifted as a youngster and just kind of fell into football, without actually really loving it. Even if you go through his social media (I know not the be all and end all, but still) he always gave the impression he really didn't give a shit about Spurs or being a footballer in general. In that interview he did after the Gillingham game he just came across as an arrogant toss pot. All of this culminating in that abomination of a loan at Norwich, and really you'd have to question if he will make it at any level unless he drastically changes his mindset.
Onomah is a bit different, I think its more a case with him that he is proper Spurs and does care, but he was just massively overrated and far too much was expected of him.
The 'problem' with him is that his playing style doesn't easily translate against the bigger bodies and better athletes in men's football. Where he was probably bigger and stronger in the youth game and could brush aside players similar to the way that Dembele does, he can't do the same against men.
I suspect that we'll see a massive improvement in his game as he grows into his body a bit more, spends some time in the gym and physically matures. I'm not writing him off just yet.