I don't understand the Chong / Greenwood hype here. They're fairly good young players and showed some promise in the U23s but I don't think they're PL quality at this point while Odoi looks clearly like Chelsea's best option on the right. IMO, It's not even a comparison, if we buy Odoi, it's not to compete with Chong and Greenwood.
I'm also kind of wary of BVB attackers - Auba, Dembele were good at BVB and good after they left as well but Mkhi, Gundogan, Gotze, Kagawa looked worldclass at BVB but failed to some extent after leaving. Who knows which bucket Sancho will fall into if he does move here.
I agree with Chong, but Greenwood is a top tier talent. Odoi is just further along in his development by virtue of being 1 year older.
As for Sancho, he was always a top talent as was Dembele. Mkhi, Gundogan, and Kagawa were a bit older. Kagawa was a wonderkid for Japan, but he wasn't an individual with talent that could dominate defenders at the European level. He was in Japan, but his playstyle wasn't as dominant with Dortmund. Really effective and technical player like any good #10, but more so on the side of someone who linked up play really well which worked wonders in that high speed Dortmund side. Back in Japan he looked Messi like, though that was also in the J League 2. Not really comparable. Gotze is a good example though.
I guess with Sancho, the best I can say is that he was marked as a top talent in a ridiculously talented group of English kids (2000 born group). He's dominated at youth international level, youth domestical level, and now the Bundesliga. Great technical ability who can run at defenders and make them look silly like Dembele. For example, compare Memphis when we bought him. He was doing great for his age with great end product, but was his technical ability top class like Sancho or Dembele? No. How about Zaha? He was incredibly influential in the Championship, but relied more on his pace than Sancho. When he came to United, it was clear that Januzaj had the better technical ability, just not the same physique, or tricky feet. Sancho is different. The ball sticks to his feet and it's objectively great technique that plays anywhere.
Have to remember he's only 18. So even if you think there is a step up to the PL, the kid is still developing and is better than almost every other 18 year old (right now) who will eventually play in the PL, but are currently either on loan or still at the u23 level.